Update CHANGELOG-EE.md for 11.5.8-ee

[ci skip]

CHANGELOG-EE.md

@@ -234,6 +234,18 @@ Please view this file on the master branch, on stable branches it's out of date.
 - Use new information-o icon for Security Dashboard.
 
 
+## 11.5.8 (2019-01-28)
+
+### Security (6 changes)
+
+- Avoid leaking unauthorized approver group members. !766
+- Sanitize user full name to clean up any URL to prevent mail clients from auto-linking URLs. !793
+- Check access rights when creating/updating ProtectedRefs.
+- Fix locked file visibility issue for private repositories.
+- Filter out non-project member approvers.
+- Remove HTTP POST in JIRA OAuth access_token endpoint.
+
+
 ## 11.5.5 (2018-12-20)
 
 - No changes.