Cross-site scripting in Contao - #VU165876
Published: November 11, 2026
Vulnerability identifier: #VU165876
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: N/A
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to execute arbitrary JavaScript in a victim's browser, potentially compromising sensitive information, modifying content, and disrupting availability.
The vulnerability exists due to improper neutralization of input in Contao's {{figure}} insert tag when nested query-string parameters populate FigureBuilder options that are merged into HTML attributes without XSS filtering. A remote user can supply crafted nested parameters and induce a victim to view the resulting content to execute scripts in the affected site's context.
Affected software
Contao
Remediation
Install security update from vendor's website.
Contao - addressed in versions 5.3.54, 5.7.17, 6.0.6