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Unpublished comments remain visible to moderators, so moderation does not prevent exposure.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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 4
https://github.com/contao/contao/commit/22505d5f79bc1a7f52e2cba5fddf6007e1f0408a
security-advisories@github.com
https://github.com/contao/contao/releases/tag/5.3.50
security-advisories@github.com
https://github.com/contao/contao/releases/tag/5.7.12
security-advisories@github.com
https://github.com/contao/contao/security/advisories/GHSA-628f-v4f6-p37r
security-advisories@github.com