Bug 2444968 (CVE-2026-28348)

Summary: CVE-2026-28348 lxml_html_clean: lxml_html_clean: Cross-Site Scripting (XSS) via CSS filter bypass
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in lxml_html_clean. The `_has_sneaky_javascript()` method incorrectly strips backslashes before checking for dangerous CSS keywords. This allows CSS Unicode escape sequences to bypass `@import` and `expression()` filters. A remote attacker could exploit this to achieve external CSS loading or Cross-Site Scripting (XSS) in older browsers, potentially leading to arbitrary script execution in the context of the user's browser.
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Bug Depends On: 2444970    
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Description OSIDB Bzimport 2026-03-05 21:02:17 UTC
lxml_html_clean is a project for HTML cleaning functionalities copied from `lxml.html.clean`. Prior to version 0.4.4, the _has_sneaky_javascript() method strips backslashes before checking for dangerous CSS keywords. This causes CSS Unicode escape sequences to bypass the @import and expression() filters, allowing external CSS loading or XSS in older browsers. This issue has been patched in version 0.4.4.