---
id: "CVE-2026-18560"
kind: "vulnerability"
aliases: ["CVE-2026-18560"]
title: "Mattermost: permission check order lets users infer flagged posts"
severity: "medium"
cvss: 4.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["mattermost", "package", "self-hosted"]
not_affected_if: ["managed-hosting"]
published_at: "2026-10-16T08:17:12+00:00"
first_seen_at: "2026-10-23T21:57:12+00:00"
updated_at: "2026-10-25T04:41:09+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-18560", "first_seen_at": "2026-10-23T21:57:12+00:00"}]
---

# Mattermost: permission check order lets users infer flagged posts

Mattermost versions 11.7.x through 11.10.0 check other conditions before verifying the caller's permissions on a flagged-post lookup. A non-content-reviewer can call the API directly and learn whether a given post has been flagged.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run the Mattermost server version check in the admin console or `mattermost version` and compare against the affected ranges
- Confirm whether content flagging is enabled in the System Console under Compliance or Content Flagging settings

## Fix

- Upgrade Mattermost server to a release that includes the MMSA-2026-00754 fix for your release line (11.7.10 or later on 11.7, 11.8.6 or later on 11.8, 11.9.2 or later on 11.9, 11.10.1 or later on 11.10); exact fixed versions unknown from the sources

## Timeline

- 2026-10-23T21:57:12+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-18560

## From the sources

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate user’s permissions before other validations which allows non-content reviewers to infer a post’s flagged status via direct API call.. Mattermost Advisory ID: MMSA-2026-00754

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_