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[ CVE-2026-107845 · Published 9 Oct 2026 ]

Contao: Cross-site scripting in the comments bundle

CVSS 9.3 EPSS <1%Fix available

[ Why it matters ]Priority signals

  • Critical severity: CVSS 9.3

[ Description ]Official description

Contao is an Open Source CMS. From version 4.0.0 until 5.3.50 and 5.7.12, an unauthenticated visitor can submit a comment whose email or website metadata is rendered without sufficient attribute and URL encoding by listComments() in comments-bundle/contao/dca/tl_comments.php. When a backend user opens the Comments module, attacker-controlled script can execute in the Contao backend origin under that user's session. Unpublished comments remain visible to moderators, so moderation does not prevent exposure. This issue is fixed in versions 5.3.50 and 5.7.12.

[ Fixes ]Fixes and patches

  • contao/comments-bundle 5.3.50Fixed version · GitHub Advisories · composer package contao/comments-bundle: upgrade to 5.3.50 or later (affected >= 4.0.0, < 5.3.50)
  • contao/comments-bundle 5.7.12Fixed version · GitHub Advisories · composer package contao/comments-bundle: upgrade to 5.7.12 or later (affected >= 5.4.0-RC1, < 5.7.12)

[ Packages ]Affected open-source packages

  • contao/comments-bundle composerAffected >= 4.0.0, < 5.3.50 · fixed in 5.3.50 · GHSA-628f-v4f6-p37r
  • contao/comments-bundle composerAffected >= 5.4.0-RC1, < 5.7.12 · fixed in 5.7.12 · GHSA-628f-v4f6-p37r

[ References ]References