Cross-site scripting in October CMS - #VU156191
Published: October 19, 2026
Vulnerability identifier: #VU156191
CSH Severity: Low
CVSS v4: 2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:H/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 privileged user to execute arbitrary JavaScript in the application origin when a victim opens a malicious SVG asset URL.
The vulnerability exists due to improper sanitization in the October CMS Editor module's editorRenameFileOrDirectory handler when renaming a non-SVG file to an SVG file. A remote privileged user can use the editor.cms_assets permission to upload malicious SVG content under an allowed non-SVG extension, rename the file to .svg without invoking Html::cleanVector, and induce a victim to open the public theme asset URL to execute arbitrary JavaScript in the application origin.
Affected software
October CMS
Remediation
Install security update from vendor's website.
October CMS - addressed in versions 3.7.18, 4.3.2