Update legacy-self-hosted-changelog.md

source/deploy/legacy-self-hosted-changelog.md

@@ -271,6 +271,10 @@ Multiple setting options were added to ``config.json``. Below is a list of the a
 
 ## Release v8.1 - [Extended Support Release](https://docs.mattermost.com/upgrade/release-definitions.html#extended-support-release-esr)
 
+- **8.1.9, released **
+  - 
+  - Fixed an issue with true-up reports sending active users and not activated users. Added **Monthly Active Users** (MAU) as part of the true-up reports.
+  - Mattermost v8.1.9 contains no database or functional changes.
 - **8.1.8, released 2024-01-09**
   - Mattermost v8.1.8 contains low to medium severity level security fixes. [Upgrading](https://docs.mattermost.com/upgrade/upgrading-mattermost-server.html) to this release is recommended. Details will be posted on our [security updates page](https://mattermost.com/security-updates/) 30 days after release as per the [Mattermost Responsible Disclosure Policy](https://mattermost.com/security-vulnerability-report/).
   - Fixed an issue with double URL encoding of Oauth redirect URI params.