Check parse_url() result in url_to_postid()

Author: SergeyBiryukov

src/wp-includes/rewrite.php

@@ -500,8 +500,19 @@ function url_to_postid( $url ) {
 	 */
 	$url = apply_filters( 'url_to_postid', $url );
 
-	$url_host      = str_replace( 'www.', '', parse_url( $url, PHP_URL_HOST ) );
-	$home_url_host = str_replace( 'www.', '', parse_url( home_url(), PHP_URL_HOST ) );
+	$url_host = parse_url( $url, PHP_URL_HOST );
+	if ( is_string( $url_host ) ) {
+		$url_host = str_replace( 'www.', '', $url_host );
+	} else {
+		return 0;
+	}
+
+	$home_url_host = parse_url( home_url(), PHP_URL_HOST );
+	if ( is_string( $home_url_host ) ) {
+		$home_url_host = str_replace( 'www.', '', $home_url_host );
+	} else {
+		return 0;
+	}
 
 	// Bail early if the URL does not belong to this site.
 	if ( $url_host && $url_host !== $home_url_host ) {

tests/phpunit/tests/rewrite.php

@@ -255,7 +255,12 @@ public function test_url_to_postid_hierarchical_with_matching_leaves() {
 		$this->assertSame( $grandchild_id_2, url_to_postid( get_permalink( $grandchild_id_2 ) ) );
 	}
 
-	public function test_url_to_postid_home_has_path() {
+	public function test_url_to_postid_url_has_only_path() {
+
+		$this->assertSame( 0, url_to_postid( '/example/' ) );
+	}
+
+	public function test_url_to_postid_home_has_only_path() {
 
 		update_option( 'home', home_url( '/example/' ) );