Improper Neutralization of Alternate XSS Syntax in Contao - #VU166054
Published: November 12, 2026
Vulnerability identifier: #VU166054
CSH Severity: Low
CVSS v4: 4.8 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-87
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to manipulate DOM properties and potentially execute arbitrary JavaScript in a victim's browser through cross-site scripting.
The vulnerability exists due to insufficient neutralization of HTML capable of DOM clobbering in Contao's default HTML sanitizer configuration when processing user-supplied content. A remote user can inject crafted HTML into content viewed by a victim to interfere with DOM properties and potentially execute scripts in the affected site's security 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