Update Changelog to include 1.8.12

Author: jaapmarcus

CHANGELOG.md

@@ -74,6 +74,13 @@ All notable changes to this project will be documented in this file.
 - Update Roundcube, Filegator, Snappy mail to the latest version
 - Update Quick Installer apps to latest version (#4594)
 
+## [1.8.12] - Service release
+
+### Security
+
+- Restrict hestiamail file permissions (todo should probably have a link here)
+- Fix roundcube permissions ( GH-4387 )
+
 ## [1.8.11] - Service release
 
 ### Features