Update Mattermost to 3.7.3 for GitLab 9.0.1
Mattermost 3.7.3 available now from https://www.mattermost.com/download/
This dot release addresses a security issue that affects all previous versions, and includes a bug fix with telemetry data collection. Upgrading to Mattermost 3.7.3 is highly recommended.
Please let me know if you have any questions. Thanks!