XSS in Contao
CVE-2026-107845
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 Unpublished comments remain visible to moderators, so moderation does not prevent exposure.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.
Vulnerability class: XSS (Cross-Site Scripting)
Published .
CVSS v3 metric
CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Contao — versions >= 4.0.0, < 5.3.50, >= 5.4.0-RC1, < 5.7.12
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-107845?
- CVE-2026-107845 is a critical-severity vulnerability in Contao, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2026-10-09.
- How severe is CVE-2026-107845?
- Critical severity. CVSS v3 base score is 9.3 out of 10.