CVE-2026-107845

Critical

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 Unpublished comments remain visible to moderators, so moderation does not prevent exposure.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

SeverityCritical

CVSS9.3

Exploit probability—

ProductContao/comments-bundle

PublishedOct 9, 2026

First seenOct 9, 2026

Weakness typeCWE-79Cross-site scripting (XSS)CWE-116CWE-116

How to fix

Update

contao/comments-bundle5.3.50, 5.7.12 or later

Affected products

Product	Affected versions	Fixed in
contao/comments-bundlePackagist	4.0.0 ≤ v < 5.3.50, 5.4.0-RC1 ≤ v < 5.7.12	5.3.50, 5.7.12

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