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MEDIUM severity

October CMS has Stored XSS in Event Log Mail PreviewGHSA-j4j5-9x6g-rgxc

MEDIUM

GHSA-j4j5-9x6g-rgxc is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in october/system. A fix is available for october/system — see the affected versions and patch details below.

Also known asCVE-2026-24907
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-j4j5-9x6g-rgxc.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs10th percentile — riskier than 10% of all scored CVEsHighest risk
0.00%0.23%0.47%0.70%0.0%0.2%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🐘october/system🐘october/system

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

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

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistoctober/system≥ 4.0.0&&< 4.1.104.1.10composer require october/system:^4.1.10
🐘Packagistoctober/systemall versions3.7.14composer require october/system:^3.7.14

Affected Products

1 product · 2 configurations
Application
octoberoctobercms
≥ 4.0.0 && ≤ 4.1.9
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for october/system, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update october/system to 4.1.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j4j5-9x6g-rgxc is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

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
O3 Security · Impact-Aware SCA

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October CMS has Stored XSS in Event Log Mail Preview