MediumGHSA-j4j5-9x6g-rgxcCVE-2026-24907

October CMS has Stored XSS in Event Log Mail Preview

Published 14 Apr 2026 · Updated 5 May 2026

Affected packages

october/systemComposer
Affected
>=4.0.0 <4.1.10
Fixed in
4.1.10
Update to the fixed version for your release line, for example:composer require october/system:^4.1.10
october/systemComposer
Affected
<3.7.14
Fixed in
3.7.14
Update to the fixed version for your release line, for example:composer require october/system:^3.7.14

Details

A stored cross-site scripting (XSS) vulnerability was identified in the Event Log mail preview feature. When viewing logged mail messages, HTML content was rendered in an iframe without proper sandboxing, allowing JavaScript execution in the viewer's browser context.

Impact

  • Stored XSS via mail template content rendered in Event Log
  • Could allow privilege escalation if a superuser views a malicious log entry
  • Requires authenticated backend access with mail template editing permissions
  • Requires a superuser to view the specific Event Log entry to trigger

Patches

The vulnerability has been patched in v3.7.14 and v4.1.10. All users are encouraged to upgrade to the latest patched version.

Workarounds

If upgrading immediately is not possible:

  • Restrict mail template editing permissions to fully trusted administrators only
  • Restrict Event Log viewing permissions to minimize exposure

References

Is GHSA-j4j5-9x6g-rgxc in any of your client repos?

Checking one package by hand is fine. Checking it across forty client projects is not. NPMscan reads the lockfiles in every GitHub repo you pick, finds each project with an affected october/system, and gives you the command that fixes it.

Scan a project free, no signupOr connect GitHub to scan every repo

References

Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.