---
title: "CVE-2026-93851: Mattermost - Stored XSS & Remote Code Execution"
description: "Mattermost 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 contain a stored XSS caused by failure to validate target post ID in Agents plugin's mention reminder, letting authenticated users cause admin browsers to send unintended API requests leading to plugin replacement and server code execution, exploit requires admin interaction."
url: https://panop.io/threat-heartbeat/CVE-2026-93851/
---

# CVE-2026-93851 Mattermost - Stored XSS & Remote Code Execution

Mattermost 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 contain a stored XSS caused by failure to validate target post ID in Agents plugin's mention reminder, letting authenticated users cause admin browsers to send unintended API requests leading to plugin replacement and server code execution, exploit requires admin interaction.

CVSS base score 8.0 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-93851)

## Details

Type

Stored XSS

Impact

Remote Code Execution, Client Script Exec

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H

Published

28 October 2026

Updated

29 October 2026

Weakness

[CWE-22](https://cwe.mitre.org/data/definitions/22.html)

## Vendor fix

Update to a version later than 11.9.1, 11.8.5, or 11.7.10.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-93851](https://nvd.nist.gov/vuln/detail/CVE-2026-93851)
- [https://mattermost.com/security-updates](https://mattermost.com/security-updates)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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