Medium · 4.3 CVE-2026-18560 EUVD-2026-102746GHSA-3m39-x8xr-762f

Improper order of authorisations in Mattermost GetFile API leads to an authenticated user to determine a post’s quarantined status

Published Oct 16, 2026 · Updated Oct 16, 2026 · Assigned by Mattermost

Description

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

Affected products

Vendor	Product	Affected	Fixed
Mattermost	Mattermost	11.10.0 – ≤ 11.10.0, 11.7.0 – ≤ 11.7.9, 11.9.0 – ≤ 11.9.1, 11.8.0 – ≤ 11.8.5	11.11.0

Advisories 1

WID-SEC-2026-4009 Mattermost: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 15, 2026

References

MMSA-2026-00754 vendor-advisory