CVE-2026-19621
Medium
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 strip action integration secrets from post payloads before broadcasting post-deletion web socket events and returning thread API responses, which allows an authenticated channel member to obtain server-side webhook URLs and authentication context from interactive-message posts via the post_deleted websocket event or the threads REST API.. Mattermost Advisory ID: MMSA-2026-00766
SeverityMedium
CVSS6.5
Exploit probability—
Product
Mattermost Server
PublishedOct 16, 2026
First seenOct 16, 2026
Weakness typeCWE-200Sensitive information exposure
How to fix
Update
- mattermost mattermost_server11.7.10, 11.8.6, 11.9.2 or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 11.7.0 ≤ v < 11.7.10, 11.8.0 ≤ v < 11.8.6, 11.9.0 ≤ v < 11.9.2, 11.10.0 | 11.7.10, 11.8.6, 11.9.2 |
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