[20260915] - Core - XSS filter bypass in InputFilter via HTML5 entity decode mismatch

Project: Joomla!
SubProject: CMS
Impact: Moderate
Severity: Moderate
Probability: Low
Versions: 1.5.0-5.4.8,6.0.0-6.1.3
Exploit type: XSS
Reported Date: 2026-08-02
Fixed Date: 2026-09-25
CVE Number: CVE-2026-92231

Description

The checkAttribute method normalized an attribute value before testing it against the "javascript:" scheme regex, however without decoding HTML5 entities beforehand, causing an XSS vector.

Affected Installs

Joomla! CMS versions 1.5.0-5.4.8, 6.0.0-6.1.3

Solution

Upgrade to version 5.4.9, 6.1.4

Contact

The JSST at the Joomla! Security Centre.

Reported By: Netanel Stern