Release v1.15.0

Security

• (Severity: Low) Harden HTML comment serialization against comment-breakout injection. Previously, programmatic Comment(...) nodes or transform-produced comment data containing sequences like --> could serialize into active HTML such as injected <img onerror>.
• (Severity: Low) Harden HTML serialization and the builder against unsafe programmatic element and attribute names. Previously, direct Node(...) usage, transform-produced attrs, or builder.element(...) calls could emit attacker-controlled markup such as injected <img onerror> by including syntax-breaking characters in a tag or attribute name.
• (Severity: Moderate) Harden JustHTML.clean_url_value(...) and clean_url_in_js_string(...) against HTML character reference smuggling such as javascript&#58..., which could bypass URL scheme validation and become an active javascript: URL after HTML attribute parsing.
• (Severity: Low) Harden URL sanitization against browser backslash normalization. Previously, “relative” URLs such as \\evil.example/x or /\\evil.example/x could survive sanitization and be interpreted by browsers as remote network requests, bypassing relative-only URL rules such as the default img[src] policy.
• (Severity: Low) Harden URL sanitization and clean_url_value(...) against malformed bracketed hosts when allowed_hosts is enabled. Previously, inputs such as https://[evil.example]/x could raise ValueError from Python’s URL parser and crash sanitization instead of being rejected.
• (Severity: Low) Harden to_markdown(html_passthrough=True) for sanitized <textarea> content. Previously, attacker-controlled </textarea> sequences could survive sanitization as text, then break out during Markdown HTML passthrough and turn into active HTML when the Markdown output was reparsed or rendered.
• (Severity: Low) Harden a[ping] sanitization. Previously, ping was treated as a single URL even though browsers interpret it as a space-separated list of URLs, so a custom policy could allow a trusted first endpoint while unintentionally preserving additional attacker-controlled ping URLs.
• (Severity: Low) Harden preserved <style> blocks in custom policies. Previously, JustHTML only neutralized HTML parser breakouts inside allowed <style> elements; resource-loading CSS such as @import, url(...), image-set(...), and legacy binding/filter constructs could still survive unchanged.
• (Severity: Low) Harden preserved <meta http-equiv=\"refresh\"> tags in custom policies. Previously, the content attribute was treated as inert text even though browsers interpret it as a client-side redirect instruction, so refresh targets could survive without any URL policy.
• (Severity: Low) Harden link[imagesrcset] sanitization in custom policies. Previously, imagesrcset was not treated as URL-bearing at all, so <link rel="preload" as="image"> could preserve attacker-controlled remote image candidates without any URL validation.
• (Severity: Low) Harden attributionsrc sanitization in custom policies. Previously, attributionsrc was not treated as URL-bearing at all, so elements such as <img> could preserve attacker-controlled attribution-reporting endpoints and trigger extra browser requests without any URL validation.
• (Severity: Low) Harden security-related attribute transforms against mixed-case attribute names in custom pipelines. Previously, transforms such as DropAttrs(...), DropUrlAttrs(...), AllowStyleAttrs(...), and MergeAttrs(...) could miss or mis-handle OnClick, SrcDoc, Href, Style, Rel, and similar mixed-case variants unless an earlier step had already normalized names to lowercase.
• (Severity: Low) Harden preserved <base href> tags in custom policies. Previously, a kept <base href="..."> could rewrite how later relative URLs resolved in the browser, bypassing per-attribute relative-only URL rules such as img[src].