From 2f4cf7bb793cfc4f05832984b8dfb299a7b2ddf3 Mon Sep 17 00:00:00 2001
From: Paul Bearne <pbearne@git.wordpress.org>
Date: Thu, 4 Dec 2025 18:46:33 -0500
Subject: [PATCH] "Add Markdown feed support with HTML to Markdown converters"

---
 src/wp-includes/default-filters.php           |   2 +
 src/wp-includes/feed-markdown.php             |  71 +++++
 src/wp-includes/functions.php                 |  25 ++
 src/wp-includes/html-to-markdown/Coerce.php   |  35 +++
 .../html-to-markdown/Configuration.php        |  80 +++++
 .../ConfigurationAwareInterface.php           |  10 +
 .../Converter/BlockquoteConverter.php         |  42 +++
 .../Converter/CodeConverter.php               |  68 +++++
 .../Converter/CommentConverter.php            |  53 ++++
 .../Converter/ConverterInterface.php          |  17 ++
 .../Converter/DefaultConverter.php            |  49 ++++
 .../Converter/DivConverter.php                |  37 +++
 .../Converter/EmphasisConverter.php           |  72 +++++
 .../Converter/HardBreakConverter.php          |  48 +++
 .../Converter/HeaderConverter.php             |  62 ++++
 .../Converter/HorizontalRuleConverter.php     |  23 ++
 .../Converter/ImageConverter.php              |  32 ++
 .../Converter/LinkConverter.php               |  77 +++++
 .../Converter/ListBlockConverter.php          |  23 ++
 .../Converter/ListItemConverter.php           |  71 +++++
 .../Converter/ParagraphConverter.php          | 108 +++++++
 .../Converter/PreformattedConverter.php       |  58 ++++
 .../Converter/TableConverter.php              | 114 +++++++
 .../Converter/TextConverter.php               |  48 +++
 src/wp-includes/html-to-markdown/Element.php  | 233 +++++++++++++++
 .../html-to-markdown/ElementInterface.php     |  50 ++++
 .../html-to-markdown/Environment.php          |  92 ++++++
 .../html-to-markdown/HtmlConverter.php        | 277 ++++++++++++++++++
 .../HtmlConverterInterface.php                |  26 ++
 .../PreConverterInterface.php                 |  10 +
 30 files changed, 1913 insertions(+)
 create mode 100644 src/wp-includes/feed-markdown.php
 create mode 100644 src/wp-includes/html-to-markdown/Coerce.php
 create mode 100644 src/wp-includes/html-to-markdown/Configuration.php
 create mode 100644 src/wp-includes/html-to-markdown/ConfigurationAwareInterface.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/BlockquoteConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/CodeConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/CommentConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/ConverterInterface.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/DefaultConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/DivConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/EmphasisConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/HardBreakConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/HeaderConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/HorizontalRuleConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/ImageConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/LinkConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/ListBlockConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/ListItemConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/ParagraphConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/PreformattedConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/TableConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Converter/TextConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/Element.php
 create mode 100644 src/wp-includes/html-to-markdown/ElementInterface.php
 create mode 100644 src/wp-includes/html-to-markdown/Environment.php
 create mode 100644 src/wp-includes/html-to-markdown/HtmlConverter.php
 create mode 100644 src/wp-includes/html-to-markdown/HtmlConverterInterface.php
 create mode 100644 src/wp-includes/html-to-markdown/PreConverterInterface.php

diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 68dccd979f2fe..2b159c1117ab5 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -416,6 +416,8 @@
 add_action( 'do_feed_rss', 'do_feed_rss', 10, 0 );
 add_action( 'do_feed_rss2', 'do_feed_rss2', 10, 1 );
 add_action( 'do_feed_atom', 'do_feed_atom', 10, 1 );
+add_action( 'do_feed_markdown', 'do_feed_markdown', 10, 1 );
+add_action( 'init', 'wp_register_markdown_feed' );
 add_action( 'do_pings', 'do_all_pings', 10, 0 );
 add_action( 'do_all_pings', 'do_all_pingbacks', 10, 0 );
 add_action( 'do_all_pings', 'do_all_enclosures', 10, 0 );
diff --git a/src/wp-includes/feed-markdown.php b/src/wp-includes/feed-markdown.php
new file mode 100644
index 0000000000000..5caca636a2470
--- /dev/null
+++ b/src/wp-includes/feed-markdown.php
@@ -0,0 +1,71 @@
+<?php
+/**
+ * Markdown Feed Template for displaying posts as Markdown text.
+ *
+ * Accessible via /?feed=markup or /feed/markup/ depending on permalink settings.
+ *
+ * @package WordPress
+ * @since 6.7.0
+ */
+
+// Output Markdown so clients can render appropriately.
+header( 'Content-Type: text/html; charset=' . get_option( 'blog_charset' ), true );
+
+// Ensure full content is used.
+// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- Used intentionally to ensure full content in feed.
+$more = 1;
+
+// Register a simple autoloader for the bundled League HTMLToMarkdown library.
+spl_autoload_register( function ( $class ) {
+	if ( 0 === strpos( $class, 'League\\HTMLToMarkdown\\' ) ) {
+		$relative = str_replace( 'League\\HTMLToMarkdown\\', '', $class );
+		$relative = str_replace( '\\', DIRECTORY_SEPARATOR, $relative );
+		$file = ABSPATH . WPINC . '/html-to-markdown/' . $relative . '.php';
+		if ( file_exists( $file ) ) {
+			require_once $file;
+		}
+	}
+} );
+
+// Create a converter instance; tune options if desired.
+$__wp_md_converter = new \League\HTMLToMarkdown\HtmlConverter( array(
+	'header_style' => 'atx',
+	'suppress_errors' => true,
+) );
+
+// Feed header as Markdown.
+echo '# ' . wp_strip_all_tags( get_bloginfo( 'name' ) ) . ' — ' . __( 'Markdown Feed', 'default' ) . "\n\n";
+$desc = get_bloginfo( 'description' );
+if ( $desc ) {
+	echo wp_strip_all_tags( $desc ) . "\n\n";
+}
+
+echo __( 'Feed URL:', 'default' ) . ' <' . esc_url_raw( get_self_link() ) . ">\n\n";
+
+if ( have_posts() ) :
+	while ( have_posts() ) :
+		the_post();
+
+		$title     = wp_strip_all_tags( get_the_title() );
+		$permalink = get_permalink();
+		$date_r    = get_post_time( 'r', true );
+		$content   = get_post_field( 'post_content', get_the_ID() );
+
+		// Post block in Markdown.
+		echo "## [" . $title . "]("
+			. $permalink . ")\n";
+		echo '*' . __( 'Published:', 'default' ) . '* ' . $date_r . "\n\n";
+
+		$html = apply_filters( 'the_content', $content );
+		$md   = $__wp_md_converter->convert( (string) $html );
+		$md   = trim( $md );
+		if ( $md !== '' ) {
+			echo $md . "\n\n";
+		}
+
+		// Separator.
+		echo "---\n\n";
+	endwhile;
+else :
+	echo __( 'No posts found.', 'default' );
+endif;
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 68a29f444fd48..dd536a6b4e75a 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -1697,6 +1697,31 @@ function do_feed_atom( $for_comments ) {
 	}
 }
 
+/**
+ * Loads the MarkDown Feed Template.
+ *
+ * A simple HTML feed that outputs post content with MarkDown preserved.
+ *
+ * @since 6.7.0
+ *
+ * @see load_template()
+ *
+ * @param bool $for_comments Unused. Present for parity with other feed handlers.
+ */
+function do_feed_markdown( $for_comments ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+
+	load_template( ABSPATH . WPINC . '/feed-markdown.php' );
+}
+
+/**
+ * Registers the Markup feed rewrite and hook.
+ *
+ * @since 6.7.0
+ */
+function wp_register_markdown_feed() {
+	add_feed( 'markdown', 'do_feed_markdown' );
+}
+
 /**
  * Displays the default robots.txt file content.
  *
diff --git a/src/wp-includes/html-to-markdown/Coerce.php b/src/wp-includes/html-to-markdown/Coerce.php
new file mode 100644
index 0000000000000..4fb0450a06183
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Coerce.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+/**
+ * @internal
+ */
+final class Coerce
+{
+    private function __construct()
+    {
+    }
+
+    /**
+     * @param mixed $val
+     */
+    public static function toString($val): string
+    {
+        switch (true) {
+            case \is_string($val):
+                return $val;
+            case \is_bool($val):
+            case \is_float($val):
+            case \is_int($val):
+            case $val === null:
+                return \strval($val);
+            case \is_object($val) && \method_exists($val, '__toString'):
+                return $val->__toString();
+            default:
+                throw new \InvalidArgumentException('Cannot coerce this value to string');
+        }
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Configuration.php b/src/wp-includes/html-to-markdown/Configuration.php
new file mode 100644
index 0000000000000..7e1d71e687e71
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Configuration.php
@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+class Configuration
+{
+    /** @var array<string, mixed> */
+    protected $config;
+
+    /**
+     * @param array<string, mixed> $config
+     */
+    public function __construct(array $config = [])
+    {
+        $this->config = $config;
+
+        $this->checkForDeprecatedOptions($config);
+    }
+
+    /**
+     * @param array<string, mixed> $config
+     */
+    public function merge(array $config = []): void
+    {
+        $this->checkForDeprecatedOptions($config);
+        $this->config = \array_replace_recursive($this->config, $config);
+    }
+
+    /**
+     * @param array<string, mixed> $config
+     */
+    public function replace(array $config = []): void
+    {
+        $this->checkForDeprecatedOptions($config);
+        $this->config = $config;
+    }
+
+    /**
+     * @param mixed $value
+     */
+    public function setOption(string $key, $value): void
+    {
+        $this->checkForDeprecatedOptions([$key => $value]);
+        $this->config[$key] = $value;
+    }
+
+    /**
+     * @param mixed|null $default
+     *
+     * @return mixed|null
+     */
+    public function getOption(?string $key = null, $default = null)
+    {
+        if ($key === null) {
+            return $this->config;
+        }
+
+        if (! isset($this->config[$key])) {
+            return $default;
+        }
+
+        return $this->config[$key];
+    }
+
+    /**
+     * @param array<string, mixed> $config
+     */
+    private function checkForDeprecatedOptions(array $config): void
+    {
+        foreach ($config as $key => $value) {
+            if ($key === 'bold_style' && $value !== '**') {
+                @\trigger_error('Customizing the bold_style option is deprecated and may be removed in the next major version', E_USER_DEPRECATED);
+            } elseif ($key === 'italic_style' && $value !== '*') {
+                @\trigger_error('Customizing the italic_style option is deprecated and may be removed in the next major version', E_USER_DEPRECATED);
+            }
+        }
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/ConfigurationAwareInterface.php b/src/wp-includes/html-to-markdown/ConfigurationAwareInterface.php
new file mode 100644
index 0000000000000..50c004c4a86aa
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/ConfigurationAwareInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+interface ConfigurationAwareInterface
+{
+    public function setConfig(Configuration $config): void;
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/BlockquoteConverter.php b/src/wp-includes/html-to-markdown/Converter/BlockquoteConverter.php
new file mode 100644
index 0000000000000..65034db129697
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/BlockquoteConverter.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class BlockquoteConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        // Contents should have already been converted to Markdown by this point,
+        // so we just need to add '>' symbols to each line.
+
+        $markdown = '';
+
+        $quoteContent = \trim($element->getValue());
+
+        $lines = \preg_split('/\r\n|\r|\n/', $quoteContent);
+        \assert(\is_array($lines));
+
+        $totalLines = \count($lines);
+
+        foreach ($lines as $i => $line) {
+            $markdown .= '> ' . $line . "\n";
+            if ($i + 1 === $totalLines) {
+                $markdown .= "\n";
+            }
+        }
+
+        return $markdown;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['blockquote'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/CodeConverter.php b/src/wp-includes/html-to-markdown/Converter/CodeConverter.php
new file mode 100644
index 0000000000000..40eb7f85a18de
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/CodeConverter.php
@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class CodeConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        $language = '';
+
+        // Checking for language class on the code block
+        $classes = $element->getAttribute('class');
+
+        if ($classes) {
+            // Since tags can have more than one class, we need to find the one that starts with 'language-'
+            $classes = \explode(' ', $classes);
+            foreach ($classes as $class) {
+                if (\strpos($class, 'language-') !== false) {
+                    // Found one, save it as the selected language and stop looping over the classes.
+                    $language = \str_replace('language-', '', $class);
+                    break;
+                }
+            }
+        }
+
+        $markdown = '';
+        $code     = \html_entity_decode($element->getChildrenAsString());
+
+        // In order to remove the code tags we need to search for them and, in the case of the opening tag
+        // use a regular expression to find the tag and the other attributes it might have
+        $code = \preg_replace('/<code\b[^>]*>/', '', $code);
+        \assert($code !== null);
+        $code = \str_replace('</code>', '', $code);
+
+        // Checking if it's a code block or span
+        if ($this->shouldBeBlock($element, $code)) {
+            // Code block detected, newlines will be added in parent
+            $markdown .= '```' . $language . "\n" . $code . "\n" . '```';
+        } else {
+            // One line of code, wrapping it on one backtick, removing new lines
+            $markdown .= '`' . \preg_replace('/\r\n|\r|\n/', '', $code) . '`';
+        }
+
+        return $markdown;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['code'];
+    }
+
+    private function shouldBeBlock(ElementInterface $element, string $code): bool
+    {
+        $parent = $element->getParent();
+        if ($parent !== null && $parent->getTagName() === 'pre') {
+            return true;
+        }
+
+        return \preg_match('/[^\s]` `/', $code) === 1;
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/CommentConverter.php b/src/wp-includes/html-to-markdown/Converter/CommentConverter.php
new file mode 100644
index 0000000000000..c69dea551d82c
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/CommentConverter.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class CommentConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        if ($this->shouldPreserve($element)) {
+            return '<!--' . $element->getValue() . '-->';
+        }
+
+        return '';
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['#comment'];
+    }
+
+    private function shouldPreserve(ElementInterface $element): bool
+    {
+        $preserve = $this->config->getOption('preserve_comments');
+        if ($preserve === true) {
+            return true;
+        }
+
+        if (\is_array($preserve)) {
+            $value = \trim($element->getValue());
+
+            return \in_array($value, $preserve, true);
+        }
+
+        return false;
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/ConverterInterface.php b/src/wp-includes/html-to-markdown/Converter/ConverterInterface.php
new file mode 100644
index 0000000000000..f10498578e010
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/ConverterInterface.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+interface ConverterInterface
+{
+    public function convert(ElementInterface $element): string;
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array;
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/DefaultConverter.php b/src/wp-includes/html-to-markdown/Converter/DefaultConverter.php
new file mode 100644
index 0000000000000..e71dd10cc06fe
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/DefaultConverter.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class DefaultConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    public const DEFAULT_CONVERTER = '_default';
+
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        // If strip_tags is false (the default), preserve tags that don't have Markdown equivalents,
+        // such as <span> nodes on their own. C14N() canonicalizes the node to a string.
+        // See: http://www.php.net/manual/en/domnode.c14n.php
+        if ($this->config->getOption('strip_tags', false)) {
+            return $element->getValue();
+        }
+
+        $markdown = \html_entity_decode($element->getChildrenAsString());
+
+        // Tables are only handled here if TableConverter is not used
+        if ($element->getTagName() === 'table') {
+            $markdown .= "\n\n";
+        }
+
+        return $markdown;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return [self::DEFAULT_CONVERTER];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/DivConverter.php b/src/wp-includes/html-to-markdown/Converter/DivConverter.php
new file mode 100644
index 0000000000000..6453a2a27c70e
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/DivConverter.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class DivConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        if ($this->config->getOption('strip_tags', false)) {
+            return $element->getValue() . "\n\n";
+        }
+
+        return \html_entity_decode($element->getChildrenAsString());
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['div'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/EmphasisConverter.php b/src/wp-includes/html-to-markdown/Converter/EmphasisConverter.php
new file mode 100644
index 0000000000000..a122f40527dac
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/EmphasisConverter.php
@@ -0,0 +1,72 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class EmphasisConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    protected function getNormTag(?ElementInterface $element): string
+    {
+        if ($element !== null && ! $element->isText()) {
+            $tag = $element->getTagName();
+            if ($tag === 'i' || $tag === 'em') {
+                return 'em';
+            }
+
+            if ($tag === 'b' || $tag === 'strong') {
+                return 'strong';
+            }
+        }
+
+        return '';
+    }
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        $tag   = $this->getNormTag($element);
+        $value = $element->getValue();
+
+        if (! \trim($value)) {
+            return $value;
+        }
+
+        if ($tag === 'em') {
+            $style = $this->config->getOption('italic_style');
+        } else {
+            $style = $this->config->getOption('bold_style');
+        }
+
+        $prefix = \ltrim($value) !== $value ? ' ' : '';
+        $suffix = \rtrim($value) !== $value ? ' ' : '';
+
+        /* If this node is immediately preceded or followed by one of the same type don't emit
+         * the start or end $style, respectively. This prevents <em>foo</em><em>bar</em> from
+         * being converted to *foo**bar* which is incorrect. We want *foobar* instead.
+         */
+        $preStyle  = $this->getNormTag($element->getPreviousSibling()) === $tag ? '' : $style;
+        $postStyle = $this->getNormTag($element->getNextSibling()) === $tag ? '' : $style;
+
+        return $prefix . $preStyle . \trim($value) . $postStyle . $suffix;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['em', 'i', 'strong', 'b'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/HardBreakConverter.php b/src/wp-includes/html-to-markdown/Converter/HardBreakConverter.php
new file mode 100644
index 0000000000000..45e89682eab1f
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/HardBreakConverter.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class HardBreakConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        $return = $this->config->getOption('hard_break') ? "\n" : "  \n";
+
+        $next = $element->getNext();
+        if ($next) {
+            $nextValue = $next->getValue();
+            if ($nextValue) {
+                if (\in_array(\substr($nextValue, 0, 2), ['- ', '* ', '+ '], true)) {
+                    $parent = $element->getParent();
+                    if ($parent && $parent->getTagName() === 'li') {
+                        $return .= '\\';
+                    }
+                }
+            }
+        }
+
+        return $return;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['br'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/HeaderConverter.php b/src/wp-includes/html-to-markdown/Converter/HeaderConverter.php
new file mode 100644
index 0000000000000..e99dfa0f435c6
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/HeaderConverter.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class HeaderConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    public const STYLE_ATX    = 'atx';
+    public const STYLE_SETEXT = 'setext';
+
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        $level = (int) \substr($element->getTagName(), 1, 1);
+        $style = $this->config->getOption('header_style', self::STYLE_SETEXT);
+
+        if (\strlen($element->getValue()) === 0) {
+            return "\n";
+        }
+
+        if (($level === 1 || $level === 2) && ! $element->isDescendantOf('blockquote') && $style === self::STYLE_SETEXT) {
+            return $this->createSetextHeader($level, $element->getValue());
+        }
+
+        return $this->createAtxHeader($level, $element->getValue());
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'];
+    }
+
+    private function createSetextHeader(int $level, string $content): string
+    {
+        $length    = \function_exists('mb_strlen') ? \mb_strlen($content, 'utf-8') : \strlen($content);
+        $underline = $level === 1 ? '=' : '-';
+
+        return $content . "\n" . \str_repeat($underline, $length) . "\n\n";
+    }
+
+    private function createAtxHeader(int $level, string $content): string
+    {
+        $prefix = \str_repeat('#', $level) . ' ';
+
+        return $prefix . $content . "\n\n";
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/HorizontalRuleConverter.php b/src/wp-includes/html-to-markdown/Converter/HorizontalRuleConverter.php
new file mode 100644
index 0000000000000..a2b1ac14a85f8
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/HorizontalRuleConverter.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class HorizontalRuleConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        return "---\n\n";
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['hr'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/ImageConverter.php b/src/wp-includes/html-to-markdown/Converter/ImageConverter.php
new file mode 100644
index 0000000000000..5cd8aec673c2a
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/ImageConverter.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class ImageConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        $src   = $element->getAttribute('src');
+        $alt   = $element->getAttribute('alt');
+        $title = $element->getAttribute('title');
+
+        if ($title !== '') {
+            // No newlines added. <img> should be in a block-level element.
+            return '![' . $alt . '](' . $src . ' "' . $title . '")';
+        }
+
+        return '![' . $alt . '](' . $src . ')';
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['img'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/LinkConverter.php b/src/wp-includes/html-to-markdown/Converter/LinkConverter.php
new file mode 100644
index 0000000000000..f0ba157f89364
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/LinkConverter.php
@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class LinkConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        $href  = $element->getAttribute('href');
+        $title = $element->getAttribute('title');
+        $text  = \trim($element->getValue(), "\t\n\r\0\x0B");
+
+        if ($title !== '') {
+            $markdown = '[' . $text . '](' . $href . ' "' . $title . '")';
+        } elseif ($href === $text && $this->isValidAutolink($href)) {
+            $markdown = '<' . $href . '>';
+        } elseif ($href === 'mailto:' . $text && $this->isValidEmail($text)) {
+            $markdown = '<' . $text . '>';
+        } else {
+            if (\stristr($href, ' ')) {
+                $href = '<' . $href . '>';
+            }
+
+            $markdown = '[' . $text . '](' . $href . ')';
+        }
+
+        if (! $href) {
+            if ($this->shouldStrip()) {
+                $markdown = $text;
+            } else {
+                $markdown = \html_entity_decode($element->getChildrenAsString());
+            }
+        }
+
+        return $markdown;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['a'];
+    }
+
+    private function isValidAutolink(string $href): bool
+    {
+        $useAutolinks = $this->config->getOption('use_autolinks');
+
+        return $useAutolinks && (\preg_match('/^[A-Za-z][A-Za-z0-9.+-]{1,31}:[^<>\x00-\x20]*/i', $href) === 1);
+    }
+
+    private function isValidEmail(string $email): bool
+    {
+        // Email validation is messy business, but this should cover most cases
+        return \filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
+    }
+
+    private function shouldStrip(): bool
+    {
+        return \boolval($this->config->getOption('strip_placeholder_links') ?? false);
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/ListBlockConverter.php b/src/wp-includes/html-to-markdown/Converter/ListBlockConverter.php
new file mode 100644
index 0000000000000..ce7b94654d65b
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/ListBlockConverter.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class ListBlockConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        return $element->getValue() . "\n";
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['ol', 'ul'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/ListItemConverter.php b/src/wp-includes/html-to-markdown/Converter/ListItemConverter.php
new file mode 100644
index 0000000000000..d71f601e157e0
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/ListItemConverter.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Coerce;
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+class ListItemConverter implements ConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    /** @var string|null */
+    protected $listItemStyle;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        // If parent is an ol, use numbers, otherwise, use dashes
+        $listType = ($parent = $element->getParent()) ? $parent->getTagName() : 'ul';
+
+        // Add spaces to start for nested list items
+        $level = $element->getListItemLevel();
+
+        $value = \trim(\implode("\n" . '    ', \explode("\n", \trim($element->getValue()))));
+
+        // If list item is the first in a nested list, add a newline before it
+        $prefix = '';
+        if ($level > 0 && $element->getSiblingPosition() === 1) {
+            $prefix = "\n";
+        }
+
+        if ($listType === 'ul') {
+            $listItemStyle          = Coerce::toString($this->config->getOption('list_item_style', '-'));
+            $listItemStyleAlternate = Coerce::toString($this->config->getOption('list_item_style_alternate', ''));
+            if (! isset($this->listItemStyle)) {
+                $this->listItemStyle = $listItemStyleAlternate ?: $listItemStyle;
+            }
+
+            if ($listItemStyleAlternate && $level === 0 && $element->getSiblingPosition() === 1) {
+                $this->listItemStyle = $this->listItemStyle === $listItemStyle ? $listItemStyleAlternate : $listItemStyle;
+            }
+
+            return $prefix . $this->listItemStyle . ' ' . $value . "\n";
+        }
+
+        if ($listType === 'ol' && ($parent = $element->getParent()) && ($start = \intval($parent->getAttribute('start')))) {
+            $number = $start + $element->getSiblingPosition() - 1;
+        } else {
+            $number = $element->getSiblingPosition();
+        }
+
+        return $prefix . $number . '. ' . $value . "\n";
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['li'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/ParagraphConverter.php b/src/wp-includes/html-to-markdown/Converter/ParagraphConverter.php
new file mode 100644
index 0000000000000..65b37a4dba8c1
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/ParagraphConverter.php
@@ -0,0 +1,108 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class ParagraphConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        $value = $element->getValue();
+
+        $markdown = '';
+
+        $lines = \preg_split('/\r\n|\r|\n/', $value);
+        \assert($lines !== false);
+
+        foreach ($lines as $line) {
+            /*
+             * Some special characters need to be escaped based on the position that they appear
+             * The following function will deal with those special cases.
+             */
+            $markdown .= $this->escapeSpecialCharacters($line);
+            $markdown .= "\n";
+        }
+
+        return \trim($markdown) !== '' ? \rtrim($markdown) . "\n\n" : '';
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['p'];
+    }
+
+    private function escapeSpecialCharacters(string $line): string
+    {
+        $line = $this->escapeFirstCharacters($line);
+        $line = $this->escapeOtherCharacters($line);
+        $line = $this->escapeOtherCharactersRegex($line);
+
+        return $line;
+    }
+
+    private function escapeFirstCharacters(string $line): string
+    {
+        $escapable = [
+            '>',
+            '- ',
+            '+ ',
+            '--',
+            '~~~',
+            '---',
+            '- - -',
+        ];
+
+        foreach ($escapable as $i) {
+            if (\strpos(\ltrim($line), $i) === 0) {
+                // Found a character that must be escaped, adding a backslash before
+                return '\\' . \ltrim($line);
+            }
+        }
+
+        return $line;
+    }
+
+    private function escapeOtherCharacters(string $line): string
+    {
+        $escapable = [
+            '<!--',
+        ];
+
+        foreach ($escapable as $i) {
+            if (($pos = \strpos($line, $i)) === false) {
+                continue;
+            }
+
+            // Found an escapable character, escaping it
+            $line = \substr_replace($line, '\\', $pos, 0);
+        }
+
+        return $line;
+    }
+
+    private function escapeOtherCharactersRegex(string $line): string
+    {
+        $regExs = [
+            // Match numbers ending on ')' or '.' that are at the beginning of the line.
+            // They will be escaped if immediately followed by a space or newline.
+            '/^[0-9]+(?=(\)|\.)( |$))/',
+        ];
+
+        foreach ($regExs as $i) {
+            if (! \preg_match($i, $line, $match)) {
+                continue;
+            }
+
+            // Matched an escapable character, adding a backslash on the string before the offending character
+            $line = \substr_replace($line, '\\', \strlen($match[0]), 0);
+        }
+
+        return $line;
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/PreformattedConverter.php b/src/wp-includes/html-to-markdown/Converter/PreformattedConverter.php
new file mode 100644
index 0000000000000..af6dd1051b3b6
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/PreformattedConverter.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class PreformattedConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        $preContent = \html_entity_decode($element->getChildrenAsString());
+        $preContent = \preg_replace('/<pre\b[^>]*>/', '', $preContent);
+        \assert($preContent !== null);
+        $preContent = \str_replace('</pre>', '', $preContent);
+
+        /*
+         * Checking for the code tag.
+         * Usually pre tags are used along with code tags. This conditional will check for already converted code tags,
+         * which use backticks, and if those backticks are at the beginning and at the end of the string it means
+         * there's no more information to convert.
+         */
+
+        $firstBacktick = \strpos(\trim($preContent), '`');
+        $lastBacktick  = \strrpos(\trim($preContent), '`');
+        if ($firstBacktick === 0 && $lastBacktick === \strlen(\trim($preContent)) - 1) {
+            return $preContent . "\n\n";
+        }
+
+        // If the execution reaches this point it means it's just a pre tag, with no code tag nested
+
+        // Empty lines are a special case
+        if ($preContent === '') {
+            return "```\n```\n\n";
+        }
+
+        // Normalizing new lines
+        $preContent = \preg_replace('/\r\n|\r|\n/', "\n", $preContent);
+        \assert(\is_string($preContent));
+
+        // Ensure there's a newline at the end
+        if (\strrpos($preContent, "\n") !== \strlen($preContent) - \strlen("\n")) {
+            $preContent .= "\n";
+        }
+
+        // Use three backticks
+        return "```\n" . $preContent . "```\n\n";
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['pre'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/TableConverter.php b/src/wp-includes/html-to-markdown/Converter/TableConverter.php
new file mode 100644
index 0000000000000..91e7180764eeb
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/TableConverter.php
@@ -0,0 +1,114 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\Coerce;
+use League\HTMLToMarkdown\Configuration;
+use League\HTMLToMarkdown\ConfigurationAwareInterface;
+use League\HTMLToMarkdown\ElementInterface;
+use League\HTMLToMarkdown\PreConverterInterface;
+
+class TableConverter implements ConverterInterface, PreConverterInterface, ConfigurationAwareInterface
+{
+    /** @var Configuration */
+    protected $config;
+
+    public function setConfig(Configuration $config): void
+    {
+        $this->config = $config;
+    }
+
+    /** @var array<string, string> */
+    private static $alignments = [
+        'left' => ':--',
+        'right' => '--:',
+        'center' => ':-:',
+    ];
+
+    /** @var array<int, string>|null */
+    private $columnAlignments = [];
+
+    /** @var string|null */
+    private $caption = null;
+
+    public function preConvert(ElementInterface $element): void
+    {
+        $tag = $element->getTagName();
+        // Only table cells and caption are allowed to contain content.
+        // Remove all text between other table elements.
+        if ($tag === 'th' || $tag === 'td' || $tag === 'caption') {
+            return;
+        }
+
+        foreach ($element->getChildren() as $child) {
+            if ($child->isText()) {
+                $child->setFinalMarkdown('');
+            }
+        }
+    }
+
+    public function convert(ElementInterface $element): string
+    {
+        $value = $element->getValue();
+
+        switch ($element->getTagName()) {
+            case 'table':
+                $this->columnAlignments = [];
+                if ($this->caption) {
+                    $side = $this->config->getOption('table_caption_side');
+                    if ($side === 'top') {
+                        $value = $this->caption . "\n" . $value;
+                    } elseif ($side === 'bottom') {
+                        $value .= $this->caption;
+                    }
+
+                    $this->caption = null;
+                }
+
+                return $value . "\n";
+            case 'caption':
+                $this->caption = \trim($value);
+
+                return '';
+            case 'tr':
+                $value .= "|\n";
+                if ($this->columnAlignments !== null) {
+                    $value .= '|' . \implode('|', $this->columnAlignments) . "|\n";
+
+                    $this->columnAlignments = null;
+                }
+
+                return $value;
+            case 'th':
+            case 'td':
+                if ($this->columnAlignments !== null) {
+                    $align = $element->getAttribute('align');
+
+                    $this->columnAlignments[] = self::$alignments[$align] ?? '---';
+                }
+
+                $value = \str_replace("\n", ' ', $value);
+                $value = \str_replace('|', Coerce::toString($this->config->getOption('table_pipe_escape') ?? '\|'), $value);
+
+                return '| ' . \trim($value) . ' ';
+            case 'thead':
+            case 'tbody':
+            case 'tfoot':
+            case 'colgroup':
+            case 'col':
+                return $value;
+            default:
+                return '';
+        }
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['table', 'tr', 'th', 'td', 'thead', 'tbody', 'tfoot', 'colgroup', 'col', 'caption'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Converter/TextConverter.php b/src/wp-includes/html-to-markdown/Converter/TextConverter.php
new file mode 100644
index 0000000000000..465dd488337f6
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Converter/TextConverter.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown\Converter;
+
+use League\HTMLToMarkdown\ElementInterface;
+
+class TextConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        $markdown = $element->getValue();
+
+        // Remove leftover \n at the beginning of the line
+        $markdown = \ltrim($markdown, "\n");
+
+        // Replace sequences of invisible characters with spaces
+        $markdown = \preg_replace('~\s+~u', ' ', $markdown);
+        \assert(\is_string($markdown));
+
+        // Escape the following characters: '*', '_', '[', ']' and '\'
+        if (($parent = $element->getParent()) && $parent->getTagName() !== 'div') {
+            $markdown = \preg_replace('~([*_\\[\\]\\\\])~u', '\\\\$1', $markdown);
+            \assert(\is_string($markdown));
+        }
+
+        $markdown = \preg_replace('~^#~u', '\\\\#', $markdown);
+        \assert(\is_string($markdown));
+
+        if ($markdown === ' ') {
+            $next = $element->getNext();
+            if (! $next || $next->isBlock()) {
+                $markdown = '';
+            }
+        }
+
+        return \htmlspecialchars($markdown, ENT_NOQUOTES, 'UTF-8');
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getSupportedTags(): array
+    {
+        return ['#text'];
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/Element.php b/src/wp-includes/html-to-markdown/Element.php
new file mode 100644
index 0000000000000..ef3ecfa9ad89c
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Element.php
@@ -0,0 +1,233 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+class Element implements ElementInterface
+{
+    /** @var \DOMNode */
+    protected $node;
+
+    /** @var ElementInterface|null */
+    private $nextCached;
+
+    /** @var \DOMNode|null */
+    private $previousSiblingCached;
+
+    public function __construct(\DOMNode $node)
+    {
+        $this->node = $node;
+
+        $this->previousSiblingCached = $this->node->previousSibling;
+    }
+
+    public function isBlock(): bool
+    {
+        switch ($this->getTagName()) {
+            case 'blockquote':
+            case 'body':
+            case 'div':
+            case 'h1':
+            case 'h2':
+            case 'h3':
+            case 'h4':
+            case 'h5':
+            case 'h6':
+            case 'hr':
+            case 'html':
+            case 'li':
+            case 'p':
+            case 'ol':
+            case 'ul':
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    public function isText(): bool
+    {
+        return $this->getTagName() === '#text';
+    }
+
+    public function isWhitespace(): bool
+    {
+        return $this->getTagName() === '#text' && \trim($this->getValue()) === '';
+    }
+
+    public function getTagName(): string
+    {
+        return $this->node->nodeName;
+    }
+
+    public function getValue(): string
+    {
+        return $this->node->nodeValue ?? '';
+    }
+
+    public function hasParent(): bool
+    {
+        return $this->node->parentNode !== null;
+    }
+
+    public function getParent(): ?ElementInterface
+    {
+        return $this->node->parentNode ? new self($this->node->parentNode) : null;
+    }
+
+    public function getNextSibling(): ?ElementInterface
+    {
+        return $this->node->nextSibling !== null ? new self($this->node->nextSibling) : null;
+    }
+
+    public function getPreviousSibling(): ?ElementInterface
+    {
+        return $this->previousSiblingCached !== null ? new self($this->previousSiblingCached) : null;
+    }
+
+    public function hasChildren(): bool
+    {
+        return $this->node->hasChildNodes();
+    }
+
+    /**
+     * @return ElementInterface[]
+     */
+    public function getChildren(): array
+    {
+        $ret = [];
+        foreach ($this->node->childNodes as $node) {
+            /** @psalm-suppress RedundantCondition */
+            \assert($node instanceof \DOMNode);
+            $ret[] = new self($node);
+        }
+
+        return $ret;
+    }
+
+    public function getNext(): ?ElementInterface
+    {
+        if ($this->nextCached === null) {
+            $nextNode = $this->getNextNode($this->node);
+            if ($nextNode !== null) {
+                $this->nextCached = new self($nextNode);
+            }
+        }
+
+        return $this->nextCached;
+    }
+
+    private function getNextNode(\DOMNode $node, bool $checkChildren = true): ?\DOMNode
+    {
+        if ($checkChildren && $node->firstChild) {
+            return $node->firstChild;
+        }
+
+        if ($node->nextSibling) {
+            return $node->nextSibling;
+        }
+
+        if ($node->parentNode) {
+            return $this->getNextNode($node->parentNode, false);
+        }
+
+        return null;
+    }
+
+    /**
+     * @param string[]|string $tagNames
+     */
+    public function isDescendantOf($tagNames): bool
+    {
+        if (! \is_array($tagNames)) {
+            $tagNames = [$tagNames];
+        }
+
+        for ($p = $this->node->parentNode; $p !== null; $p = $p->parentNode) {
+            if (\in_array($p->nodeName, $tagNames, true)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public function setFinalMarkdown(string $markdown): void
+    {
+        if ($this->node->ownerDocument === null) {
+            throw new \RuntimeException('Unowned node');
+        }
+
+        if ($this->node->parentNode === null) {
+            throw new \RuntimeException('Cannot setFinalMarkdown() on a node without a parent');
+        }
+
+        $markdownNode = $this->node->ownerDocument->createTextNode($markdown);
+        $this->node->parentNode->replaceChild($markdownNode, $this->node);
+    }
+
+    public function getChildrenAsString(): string
+    {
+        return $this->node->C14N();
+    }
+
+    public function getSiblingPosition(): int
+    {
+        $position = 0;
+
+        $parent = $this->getParent();
+        if ($parent === null) {
+            return $position;
+        }
+
+        // Loop through all nodes and find the given $node
+        foreach ($parent->getChildren() as $currentNode) {
+            if (! $currentNode->isWhitespace()) {
+                $position++;
+            }
+
+            // TODO: Need a less-buggy way of comparing these
+            // Perhaps we can somehow ensure that we always have the exact same object and use === instead?
+            if ($this->equals($currentNode)) {
+                break;
+            }
+        }
+
+        return $position;
+    }
+
+    public function getListItemLevel(): int
+    {
+        $level  = 0;
+        $parent = $this->getParent();
+
+        while ($parent !== null && $parent->hasParent()) {
+            if ($parent->getTagName() === 'li') {
+                $level++;
+            }
+
+            $parent = $parent->getParent();
+        }
+
+        return $level;
+    }
+
+    public function getAttribute(string $name): string
+    {
+        if ($this->node instanceof \DOMElement) {
+            return $this->node->getAttribute($name);
+        }
+
+        return '';
+    }
+
+    public function equals(ElementInterface $element): bool
+    {
+        if ($element instanceof self) {
+            return $element->node === $this->node;
+        }
+
+        return false;
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/ElementInterface.php b/src/wp-includes/html-to-markdown/ElementInterface.php
new file mode 100644
index 0000000000000..d8477cfae432d
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/ElementInterface.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+interface ElementInterface
+{
+    public function isBlock(): bool;
+
+    public function isText(): bool;
+
+    public function isWhitespace(): bool;
+
+    public function getTagName(): string;
+
+    public function getValue(): string;
+
+    public function hasParent(): bool;
+
+    public function getParent(): ?ElementInterface;
+
+    public function getNextSibling(): ?ElementInterface;
+
+    public function getPreviousSibling(): ?ElementInterface;
+
+    /**
+     * @param string|string[] $tagNames
+     */
+    public function isDescendantOf($tagNames): bool;
+
+    public function hasChildren(): bool;
+
+    /**
+     * @return ElementInterface[]
+     */
+    public function getChildren(): array;
+
+    public function getNext(): ?ElementInterface;
+
+    public function getSiblingPosition(): int;
+
+    public function getChildrenAsString(): string;
+
+    public function setFinalMarkdown(string $markdown): void;
+
+    public function getListItemLevel(): int;
+
+    public function getAttribute(string $name): string;
+}
diff --git a/src/wp-includes/html-to-markdown/Environment.php b/src/wp-includes/html-to-markdown/Environment.php
new file mode 100644
index 0000000000000..7ea19d4107b36
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/Environment.php
@@ -0,0 +1,92 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+use League\HTMLToMarkdown\Converter\BlockquoteConverter;
+use League\HTMLToMarkdown\Converter\CodeConverter;
+use League\HTMLToMarkdown\Converter\CommentConverter;
+use League\HTMLToMarkdown\Converter\ConverterInterface;
+use League\HTMLToMarkdown\Converter\DefaultConverter;
+use League\HTMLToMarkdown\Converter\DivConverter;
+use League\HTMLToMarkdown\Converter\EmphasisConverter;
+use League\HTMLToMarkdown\Converter\HardBreakConverter;
+use League\HTMLToMarkdown\Converter\HeaderConverter;
+use League\HTMLToMarkdown\Converter\HorizontalRuleConverter;
+use League\HTMLToMarkdown\Converter\ImageConverter;
+use League\HTMLToMarkdown\Converter\LinkConverter;
+use League\HTMLToMarkdown\Converter\ListBlockConverter;
+use League\HTMLToMarkdown\Converter\ListItemConverter;
+use League\HTMLToMarkdown\Converter\ParagraphConverter;
+use League\HTMLToMarkdown\Converter\PreformattedConverter;
+use League\HTMLToMarkdown\Converter\TextConverter;
+
+final class Environment
+{
+    /** @var Configuration */
+    protected $config;
+
+    /** @var ConverterInterface[] */
+    protected $converters = [];
+
+    /**
+     * @param array<string, mixed> $config
+     */
+    public function __construct(array $config = [])
+    {
+        $this->config = new Configuration($config);
+        $this->addConverter(new DefaultConverter());
+    }
+
+    public function getConfig(): Configuration
+    {
+        return $this->config;
+    }
+
+    public function addConverter(ConverterInterface $converter): void
+    {
+        if ($converter instanceof ConfigurationAwareInterface) {
+            $converter->setConfig($this->config);
+        }
+
+        foreach ($converter->getSupportedTags() as $tag) {
+            $this->converters[$tag] = $converter;
+        }
+    }
+
+    public function getConverterByTag(string $tag): ConverterInterface
+    {
+        if (isset($this->converters[$tag])) {
+            return $this->converters[$tag];
+        }
+
+        return $this->converters[DefaultConverter::DEFAULT_CONVERTER];
+    }
+
+    /**
+     * @param array<string, mixed> $config
+     */
+    public static function createDefaultEnvironment(array $config = []): Environment
+    {
+        $environment = new static($config);
+
+        $environment->addConverter(new BlockquoteConverter());
+        $environment->addConverter(new CodeConverter());
+        $environment->addConverter(new CommentConverter());
+        $environment->addConverter(new DivConverter());
+        $environment->addConverter(new EmphasisConverter());
+        $environment->addConverter(new HardBreakConverter());
+        $environment->addConverter(new HeaderConverter());
+        $environment->addConverter(new HorizontalRuleConverter());
+        $environment->addConverter(new ImageConverter());
+        $environment->addConverter(new LinkConverter());
+        $environment->addConverter(new ListBlockConverter());
+        $environment->addConverter(new ListItemConverter());
+        $environment->addConverter(new ParagraphConverter());
+        $environment->addConverter(new PreformattedConverter());
+        $environment->addConverter(new TextConverter());
+
+        return $environment;
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/HtmlConverter.php b/src/wp-includes/html-to-markdown/HtmlConverter.php
new file mode 100644
index 0000000000000..944cb081b6ef4
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/HtmlConverter.php
@@ -0,0 +1,277 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+/**
+ * A helper class to convert HTML to Markdown.
+ *
+ * @author Colin O'Dell <colinodell@gmail.com>
+ * @author Nick Cernis <nick@cern.is>
+ *
+ * @link https://github.com/thephpleague/html-to-markdown/ Latest version on GitHub.
+ *
+ * @license http://www.opensource.org/licenses/mit-license.php MIT
+ */
+class HtmlConverter implements HtmlConverterInterface
+{
+    /** @var Environment */
+    protected $environment;
+
+    /**
+     * Constructor
+     *
+     * @param Environment|array<string, mixed> $options Environment object or configuration options
+     */
+    public function __construct($options = [])
+    {
+        if ($options instanceof Environment) {
+            $this->environment = $options;
+        } elseif (\is_array($options)) {
+            $defaults = [
+                'header_style' => 'setext', // Set to 'atx' to output H1 and H2 headers as # Header1 and ## Header2
+                'suppress_errors' => true, // Set to false to show warnings when loading malformed HTML
+                'strip_tags' => false, // Set to true to strip tags that don't have markdown equivalents. N.B. Strips tags, not their content. Useful to clean MS Word HTML output.
+                'strip_placeholder_links' => false, // Set to true to remove <a> that doesn't have href.
+                'bold_style' => '**', // DEPRECATED: Set to '__' if you prefer the underlined style
+                'italic_style' => '*', // DEPRECATED: Set to '_' if you prefer the underlined style
+                'remove_nodes' => '', // space-separated list of dom nodes that should be removed. example: 'meta style script'
+                'hard_break' => false, // Set to true to turn <br> into `\n` instead of `  \n`
+                'list_item_style' => '-', // Set the default character for each <li> in a <ul>. Can be '-', '*', or '+'
+                'preserve_comments' => false, // Set to true to preserve comments, or set to an array of strings to preserve specific comments
+                'use_autolinks' => true, // Set to true to use simple link syntax if possible. Will always use []() if set to false
+                'table_pipe_escape' => '\|', // Replacement string for pipe characters inside markdown table cells
+                'table_caption_side' => 'top', // Set to 'top' or 'bottom' to show <caption> content before or after table, null to suppress
+            ];
+
+            $this->environment = Environment::createDefaultEnvironment($defaults);
+
+            $this->environment->getConfig()->merge($options);
+        }
+    }
+
+    public function getEnvironment(): Environment
+    {
+        return $this->environment;
+    }
+
+    public function getConfig(): Configuration
+    {
+        return $this->environment->getConfig();
+    }
+
+    /**
+     * Convert
+     *
+     * @see HtmlConverter::convert
+     *
+     * @return string The Markdown version of the html
+     */
+    public function __invoke(string $html): string
+    {
+        return $this->convert($html);
+    }
+
+    /**
+     * Convert
+     *
+     * Loads HTML and passes to getMarkdown()
+     *
+     * @return string The Markdown version of the html
+     *
+     * @throws \InvalidArgumentException|\RuntimeException
+     */
+    public function convert(string $html): string
+    {
+        if (\trim($html) === '') {
+            return '';
+        }
+
+        $document = $this->createDOMDocument($html);
+
+        // Work on the entire DOM tree (including head and body)
+        if (! ($root = $document->getElementsByTagName('html')->item(0))) {
+            throw new \InvalidArgumentException('Invalid HTML was provided');
+        }
+
+        $rootElement = new Element($root);
+        $this->convertChildren($rootElement);
+
+        // Store the now-modified DOMDocument as a string
+        $markdown = $document->saveHTML();
+
+        if ($markdown === false) {
+            throw new \RuntimeException('Unknown error occurred during HTML to Markdown conversion');
+        }
+
+        return $this->sanitize($markdown);
+    }
+
+    private function createDOMDocument(string $html): \DOMDocument
+    {
+        $document = new \DOMDocument();
+
+        if ($this->getConfig()->getOption('suppress_errors')) {
+            // Suppress conversion errors (from http://bit.ly/pCCRSX)
+            \libxml_use_internal_errors(true);
+        }
+
+        // Hack to load utf-8 HTML (from http://bit.ly/pVDyCt)
+        $document->loadHTML('<?xml encoding="UTF-8">' . $html);
+        $document->encoding = 'UTF-8';
+
+        $this->replaceMisplacedComments($document);
+
+        if ($this->getConfig()->getOption('suppress_errors')) {
+            \libxml_clear_errors();
+        }
+
+        return $document;
+    }
+
+    /**
+     * Finds any comment nodes outside <html> element and moves them into <body>.
+     *
+     * @see https://github.com/thephpleague/html-to-markdown/issues/212
+     * @see https://3v4l.org/7bC33
+     */
+    private function replaceMisplacedComments(\DOMDocument $document): void
+    {
+        // Find ny comment nodes at the root of the document.
+        $misplacedComments = (new \DOMXPath($document))->query('/comment()');
+        if ($misplacedComments === false) {
+            return;
+        }
+
+        $body = $document->getElementsByTagName('body')->item(0);
+        if ($body === null) {
+            return;
+        }
+
+        // Loop over comment nodes in reverse so we put them inside <body> in
+        // their original order.
+        for ($index = $misplacedComments->length - 1; $index >= 0; $index--) {
+            if ($body->firstChild === null) {
+                $body->insertBefore($misplacedComments[$index]);
+            } else {
+                $body->insertBefore($misplacedComments[$index], $body->firstChild);
+            }
+        }
+    }
+
+    /**
+     * Convert Children
+     *
+     * Recursive function to drill into the DOM and convert each node into Markdown from the inside out.
+     *
+     * Finds children of each node and convert those to #text nodes containing their Markdown equivalent,
+     * starting with the innermost element and working up to the outermost element.
+     */
+    private function convertChildren(ElementInterface $element): void
+    {
+        // Don't convert HTML code inside <code> and <pre> blocks to Markdown - that should stay as HTML
+        // except if the current node is a code tag, which needs to be converted by the CodeConverter.
+        if ($element->isDescendantOf(['pre', 'code']) && $element->getTagName() !== 'code') {
+            return;
+        }
+
+        // Give converter a chance to inspect/modify the DOM before children are converted
+        $converter = $this->environment->getConverterByTag($element->getTagName());
+        if ($converter instanceof PreConverterInterface) {
+            $converter->preConvert($element);
+        }
+
+        // If the node has children, convert those to Markdown first
+        if ($element->hasChildren()) {
+            foreach ($element->getChildren() as $child) {
+                $this->convertChildren($child);
+            }
+        }
+
+        // Now that child nodes have been converted, convert the original node
+        $markdown = $this->convertToMarkdown($element);
+
+        // Create a DOM text node containing the Markdown equivalent of the original node
+
+        // Replace the old $node e.g. '<h3>Title</h3>' with the new $markdown_node e.g. '### Title'
+        $element->setFinalMarkdown($markdown);
+    }
+
+    /**
+     * Convert to Markdown
+     *
+     * Converts an individual node into a #text node containing a string of its Markdown equivalent.
+     *
+     * Example: An <h3> node with text content of 'Title' becomes a text node with content of '### Title'
+     *
+     * @return string The converted HTML as Markdown
+     */
+    protected function convertToMarkdown(ElementInterface $element): string
+    {
+        $tag = $element->getTagName();
+
+        // Strip nodes named in remove_nodes
+        $tagsToRemove = \explode(' ', Coerce::toString($this->getConfig()->getOption('remove_nodes') ?? ''));
+        if (\in_array($tag, $tagsToRemove, true)) {
+            return '';
+        }
+
+        $converter = $this->environment->getConverterByTag($tag);
+
+        return $converter->convert($element);
+    }
+
+    protected function sanitize(string $markdown): string
+    {
+        $markdown = \html_entity_decode($markdown, ENT_QUOTES, 'UTF-8');
+        $markdown = \preg_replace('/<!DOCTYPE [^>]+>/', '', $markdown); // Strip doctype declaration
+        \assert($markdown !== null);
+        $markdown = \trim($markdown); // Remove blank spaces at the beggining of the html
+
+        /*
+         * Removing unwanted tags. Tags should be added to the array in the order they are expected.
+         * XML, html and body opening tags should be in that order. Same case with closing tags
+         */
+        $unwanted = ['<?xml encoding="UTF-8">', '<html>', '</html>', '<body>', '</body>', '<head>', '</head>', '&#xD;'];
+
+        foreach ($unwanted as $tag) {
+            if (\strpos($tag, '/') === false) {
+                // Opening tags
+                if (\strpos($markdown, $tag) === 0) {
+                    $markdown = \substr($markdown, \strlen($tag));
+                }
+            } else {
+                // Closing tags
+                if (\strpos($markdown, $tag) === \strlen($markdown) - \strlen($tag)) {
+                    $markdown = \substr($markdown, 0, -\strlen($tag));
+                }
+            }
+        }
+
+        return \trim($markdown, "\n\r\0\x0B");
+    }
+
+    /**
+     * Pass a series of key-value pairs in an array; these will be passed
+     * through the config and set.
+     * The advantage of this is that it can allow for static use (IE in Laravel).
+     * An example being:
+     *
+     * HtmlConverter::setOptions(['strip_tags' => true])->convert('<h1>test</h1>');
+     *
+     * @param array<string, mixed> $options
+     *
+     * @return $this
+     */
+    public function setOptions(array $options)
+    {
+        $config = $this->getConfig();
+
+        foreach ($options as $key => $option) {
+            $config->setOption($key, $option);
+        }
+
+        return $this;
+    }
+}
diff --git a/src/wp-includes/html-to-markdown/HtmlConverterInterface.php b/src/wp-includes/html-to-markdown/HtmlConverterInterface.php
new file mode 100644
index 0000000000000..5c7e9eb65e810
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/HtmlConverterInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+/**
+ * Interface for an HTML-to-Markdown converter.
+ *
+ * @author Colin O'Dell <colinodell@gmail.com>
+ *
+ * @link https://github.com/thephpleague/html-to-markdown/ Latest version on GitHub.
+ *
+ * @license http://www.opensource.org/licenses/mit-license.php MIT
+ */
+interface HtmlConverterInterface
+{
+    /**
+     * Convert the given $html to Markdown
+     *
+     * @return string The Markdown version of the html
+     *
+     * @throws \InvalidArgumentException
+     */
+    public function convert(string $html): string;
+}
diff --git a/src/wp-includes/html-to-markdown/PreConverterInterface.php b/src/wp-includes/html-to-markdown/PreConverterInterface.php
new file mode 100644
index 0000000000000..f835086ef7dcc
--- /dev/null
+++ b/src/wp-includes/html-to-markdown/PreConverterInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\HTMLToMarkdown;
+
+interface PreConverterInterface
+{
+    public function preConvert(ElementInterface $element): void;
+}