#VU122291 Stored cross-site scripting in Six Apart Ltd products - CVE-2026-21393
Published: February 4, 2026
Vulnerability identifier: #VU122291
Vulnerability risk: Low
CVSSv4.0: 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/E:U/U:Clear
CVE-ID: CVE-2026-21393
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Movable Type
Movable Type Advanced
Movable Type Premium
Movable Type Premium (Advanced Edition)
Movable Type Cloud Edition
Movable Type Premium Cloud Edition
Movable Type
Movable Type Advanced
Movable Type Premium
Movable Type Premium (Advanced Edition)
Movable Type Cloud Edition
Movable Type Premium Cloud Edition
Software vendor:
Six Apart Ltd
Six Apart Ltd
Description
The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.
The vulnerability exists due to insufficient sanitization of user-supplied data in Edit Comment. A remote user can inject and execute arbitrary HTML and script code in user's browser in context of vulnerable website.
Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.
Remediation
Install updates from vendor's website.