Mattermost Security Updates August 13, 2026

What does this MR do and why?

Update Mattermost from version 10.11.20 to 10.11.23. As there was recently a backport commit (!9623 (merged)) to the old stable, it seems there is still a release planed. As Mattermost 10.11.22 contains high severity level security fixes, it would be nice, if the next 18.11 release includes it.

The full changelog for this release can be found here.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The original MR has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).