Vulnerability · Published Oct 9, 2026 · Assigned by GitHub_M

CVE-2026-107845Contao: Cross-site scripting in the comments bundle

Critical 9.3

In plain English

A critical-severity cross-site scripting in contao from contao. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.3Critical

Exploit odds (30 days)0.3%top 79.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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 Unpublished comments remain visible to moderators, so moderation does not prevent exposure.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

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Packagist	contao/comments-bundle	5.3.50	GHSA-628f-v4f6-p37r
Packagist	contao/comments-bundle	5.7.12	GHSA-628f-v4f6-p37r

Affected products (as reported)

Vendor	Product	Versions
contao	contao	>= 4.0.0, < 5.3.50>= 5.4.0-RC1, < 5.7.12

Weakness: CWE-79, CWE-116 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

References

https://github.com/contao/contao/security/advisories/GHSA-628f-v4f6-p37r x_refsource_CONFIRM
https://github.com/contao/contao/commit/22505d5f79bc1a7f52e2cba5fddf6007e1f0408a x_refsource_MISC
https://github.com/contao/contao/releases/tag/5.3.50 x_refsource_MISC
https://github.com/contao/contao/releases/tag/5.7.12 x_refsource_MISC