CVE-2026-107845: Contao

Critical severity, CVSS 9.3. EPSS: 0.3% chance of exploitation in the next 30 days.

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 Unpublished comments remain visible to moderators, so moderation does not prevent exposure.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

Affected products

• Contao Contao: from 4.0.0, before 5.3.50 (fixed in 5.3.50); from 5.4.0-RC1, before 5.7.12 (fixed in 5.7.12)

Published 2026-10-09. Last modified 2026-10-09.