CVE-2026-107845

Contao: Cross-site scripting in the comments bundle

State: Published
Severity: 9.3 Critical
Published: Oct 9, 2026
Updated: Oct 9, 2026
Reserved: Oct 8, 2026

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 Unpublished comments remain visible to moderators, so moderation does not prevent exposure.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.

Scores

CVSS	Score	Vector	Source
3.1	9.3 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-116 Improper Encoding or Escaping of Output

Affected Products

Product	Versions
contaocontao	>= 4.0.0, < 5.3.50Affected >= 5.4.0-RC1, < 5.7.12Affected

References

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