# CVE-2026-24907: October CMS has Stored XSS via Event Log Mail Preview

> Attackers can execute arbitrary JavaScript in admin browsers via unsandboxed HTML in the Event Log mail preview, potentially leading to account takeover.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 14 Apr 2026
- **Updated:** 14 Apr 2026
- **Also known as:** GHSA-j4j5-9x6g-rgxc

## What is CVE-2026-24907?

CVE-2026-24907 is a medium-severity cross-site scripting vulnerability in Octobercms October, published on 14 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

October is a Content Management System (CMS) and web platform. Versions prior to 3.7.14 and 4.1.10 contain a stored cross-site scripting (XSS) vulnerability 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. This issue has been fixed in versions 3.7.14 and 4.1.10. If users are unable to update immediately, workarounds include restricting mail template editing permissions to fully trusted administrators only and restricting Event Log viewing permissions to minimize exposure.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-24907?

4 open source packages ship an affected version, including october/system. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `october/system` | Packagist | All versions | 3.7.14 |
| `october/system` | Packagist | All versions | 3.7.14 |
| `october/system` | Packagist | From 4.0.0 | 4.1.10 |
| `october/system` | Packagist | From 4.0.0 | 4.1.10 |

Products: Octobercms October.

## How do I fix CVE-2026-24907?

Upgrade october/system to a fixed version for your release line: 3.7.14 or 4.1.10.

## Is CVE-2026-24907 being exploited?

There is no known exploitation of CVE-2026-24907 in the wild and no public exploit code.

## Other vulnerabilities in Octobercms October

- [CVE-2021-32648](https://insights.sbomify.com/CVE-2021-32648/): October CMS Improper Authentication (high 8.2, exploited in the wild)
- [CVE-2021-3311](https://insights.sbomify.com/CVE-2021-3311/): October CMS Session ID not invalidated after logout (critical 9.8)
- [CVE-2017-1000194](https://insights.sbomify.com/CVE-2017-1000194/): October CMS File Upload Vulnerability (critical 9.8)
- [CVE-2017-1000196](https://insights.sbomify.com/CVE-2017-1000196/): Code injection in n/a (critical 9.8)
- [CVE-2017-1000197](https://insights.sbomify.com/CVE-2017-1000197/): Path traversal in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-24907 and fix it if it is affected.

What it is: CVE-2026-24907 is a medium-severity cross-site scripting vulnerability in Octobercms October, published on 14 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-24907 in the wild and no public exploit code.

Affected packages and fixed versions:
- october/system (Packagist): affected all versions; fixed in 3.7.14
- october/system (Packagist): affected all versions; fixed in 3.7.14
- october/system (Packagist): affected from 4.0.0; fixed in 4.1.10
- october/system (Packagist): affected from 4.0.0; fixed in 4.1.10

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-24907/ (Markdown: https://insights.sbomify.com/CVE-2026-24907/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-24907
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-24907
- OSV: https://osv.dev/vulnerability/CVE-2026-24907

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-24907/
Summaries are generated and may contain mistakes; the official description above is the record.