lxml_html_clean changelog

0.4.6 (2026-10-26)

Bugs fixed

  • Fixed a ReDoS (regular expression denial of service) vulnerability in the CSS expression() sanitizer. The pattern expression\s*\(.*?\) with re.S was quadratic when input contained many expression( tokens without a closing parenthesis. The body is now bounded to 1024 characters; longer bodies are handled fail-closed by _has_sneaky_javascript(), which drops the entire style. Reported by Brian Willows.

  • Fixed a ReDoS vulnerability in the conditional comment detector used when comments=False. The pattern \[if\s+.*?]\s*> with re.S was quadratic when comment text contained many [if tokens without a closing ]>. Replaced with a linear two-pass search. Reported by Brian Willows.

  • Fixed a ReDoS vulnerability in the CSS comment stripper. The pattern /\*.*?\*/ with re.S was quadratic when style content contained many /* tokens without a closing */. Replaced with a linear str.find()-based scan. Reachable under default configuration via <style> element content.

  • Fixed a ReDoS vulnerability in the image data-URL scanner. The pattern data:image/(.+?);base64, was quadratic when input contained many data:image/ tokens without a following ;base64,. The MIME subtype body is now bounded to 255 characters. Reachable under default configuration via link attributes and <style> element content.

0.4.5 (2026-05-20)

Bugs fixed

  • Fixed a security vulnerability where javascript: URLs in xlink:href attributes were not sanitized when``safe_attrs_only=False``, allowing cross-site scripting (XSS) attacks. The fix requires lxml>=6.1.1, which adds xlink:href to the set of link attributes iterated by rewrite_links(). Reported by Guillem Lefait (@glefait).

0.4.4 (2026-02-26)

Bugs fixed

  • Fixed a bug where Unicode escapes in CSS were not properly decoded before security checks. This prevents attackers from bypassing filters using escape sequences. (CVE-2026-28348)

  • Fixed a security issue where <base> tags could be used for URL hijacking attacks. The <base> tag is now automatically removed whenever the <head> tag is removed (via page_structure=True or manual configuration), as <base> must be inside <head> according to HTML specifications. (CVE-2026-28350)

0.4.3 (2025-10-02)

Maintenance

  • Tests updated to work correctly with new lxml and libxml2 releases.

  • Python 3.6 and 3.7 are no longer tested.

  • Improved documentation about CSS removal behavior.

0.4.2 (2025-04-09)

Bugs fixed

  • lxml_html_clean now correctly handles HTML input as bytes as it did before the 0.2.0 release.

0.4.1 (2024-11-15)

Bugs fixed

  • Removed superfluous debug prints.

0.4.0 (2024-11-12)

Bugs fixed

  • The Cleaner() now scans for hidden JavaScript code embedded within CSS comments. In certain contexts, such as within <svg> or <math> tags, <style> tags may lose their intended function, allowing comments like /* foo */ to potentially be executed by the browser. If a suspicious content is detected, only the comment is removed. (CVE-2024-52595)

0.3.1 (2024-10-09)

Features added

  • Do not parse URL addresses when it is not necessary.

0.3.0 (2024-10-09)

Features added

  • Parsing of URL addresses has been enhanced and Cleaner removes ambiguous URLs.

0.2.2 (2024-08-30)

Bugs fixed

  • sdist now includes all test files and changelog.

0.2.1 (2024-08-29)

Bugs fixed

  • Memory efficiency is now much better for HTML pages where cleaner removes a lot of elements. (#14)

0.2.0 (2024-07-29)

Features added

  • ASCII control characters (except HT, VT, CR and LF) are now removed from string inputs before they’re parsed by lxml/libxml2.

0.1.1 (2024-04-05)

Bugs fixed

  • Regular expresion for image data URLs now supports multiple data URLs on a single line.

0.1.0 (2024-02-26)

First official release of the split project.

Relevant changes from lxml project before the split

This part contains releases of lxml project containing important changes related to HTML Cleaner functionalities.

5.1.0 (2024-01-05)

Bugs fixed

  • The HTML Cleaner() interpreted an accidentally provided string parameter for the host_whitelist as list of characters and silently failed to reject any hosts. Passing a non-collection is now rejected.

4.9.3 (2023-07-05)

Bugs fixed

  • A memory leak in lxml.html.clean was resolved by switching to Cython 0.29.34+.

  • URL checking in the HTML cleaner was improved. Patch by Tim McCormack.

4.6.5 (2021-12-12)

Bugs fixed

  • A vulnerability (GHSL-2021-1038) in the HTML cleaner allowed sneaking script content through SVG images (CVE-2021-43818).

  • A vulnerability (GHSL-2021-1037) in the HTML cleaner allowed sneaking script content through CSS imports and other crafted constructs (CVE-2021-43818).

4.6.3 (2021-03-21)

Bugs fixed

  • A vulnerability (CVE-2021-28957) was discovered in the HTML Cleaner by Kevin Chung, which allowed JavaScript to pass through. The cleaner now removes the HTML5 formaction attribute.

4.6.2 (2020-11-26)

Bugs fixed

  • A vulnerability (CVE-2020-27783) was discovered in the HTML Cleaner by Yaniv Nizry, which allowed JavaScript to pass through. The cleaner now removes more sneaky “style” content.

4.6.1 (2020-10-18)

Bugs fixed

  • A vulnerability was discovered in the HTML Cleaner by Yaniv Nizry, which allowed JavaScript to pass through. The cleaner now removes more sneaky “style” content.

4.5.2 (2020-07-09)

Bugs fixed

  • Cleaner() now validates that only known configuration options can be set.

  • Cleaner.clean_html() discarded comments and PIs regardless of the corresponding configuration option, if remove_unknown_tags was set.

4.2.5 (2018-09-09)

Bugs fixed

  • Javascript URLs that used URL escaping were not removed by the HTML cleaner. Security problem found by Omar Eissa. (CVE-2018-19787)

4.0.0 (2017-09-17)

Features added

  • The modules lxml.builder, lxml.html.diff and lxml.html.clean are also compiled using Cython in order to speed them up.