Update CHANGELOG-EE.md for 11.7.8-ee

[ci skip]

CHANGELOG-EE.md

@@ -230,6 +230,14 @@ Please view this file on the master branch, on stable branches it's out of date.
 - Creates an EE component for the pipeline graph.
 
 
+## 11.7.8 (2019-03-26)
+
+### Security (2 changes)
+
+- Geo - Improve security while redirecting user back to the secondary after a logout & re-login via the primary.
+- Check label_ids parent when updating issue board.
+
+
 ## 11.7.7 (2019-03-19)
 
 - No changes.