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6.1

Firefox can mis‑rewrite CSS namespaces when pasting style tags

published 4 days ago
Summary

When a user pastes a <style> tag into a rich‑text editor in Firefox or Firefox ESR, the built‑in CSS cleaning code may change the @namespace rule incorrectly. This can cause unexpected styling or allow crafted content to affect the page layout. Upgrade to the latest Firefox release, which includes a fix for this behavior.

What to do
  • Update cleanstart firefox to version 71.0.1-r0.
  • Update cleanstart firefox-esr to version 68.4.1-r0.
Affected software
Ecosystem VendorProductAffected versions
CleanStart cleanstart firefox < 71.0.1-r0
Fix: upgrade to 71.0.1-r0
CleanStart cleanstart firefox-esr < 68.4.1-r0
Fix: upgrade to 68.4.1-r0
Original advisory text
When pasting a &lt;style&gt; tag from the clipboard into a rich text editor, the CSS sanitizer incorrectly rewrites a @namespace rule
CVE-2019-17016 affects multiple packages. When pasting a &lt;style&gt; tag from the clipboard into a rich text editor, the CSS sanitizer incorrectly rewrites a @namespace rule. See references for individual vulnerability details.
Fix within
Internet-facing 60 days
Internal At next upgrade
  • Not known to be exploited
  • Needs hands-on effort to exploit (estimated)
  • Gives an attacker partial control (estimated)
Severity
6.1 Medium
Timeline
Published31 Oct 2026
Updated31 Oct 2026
First seen31 Oct 2026
Sources
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