Update CHANGELOG-EE.md for 13.3.3-ee

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CHANGELOG-EE.md

 Please view this file on the master branch, on stable branches it's out of date.
+## 13.3.3 (2020-09-02)
+
+### Security (2 changes)
+
+- Sanitize vulnerability history comment.
+- Fix displaying epics visibility in issue sidebar.
+
+
 ## 13.3.2 (2020-08-28)
 - No changes.

ee/changelogs/unreleased/security-219378-xss-on-vulnerability-history.yml

----
-title: Sanitize vulnerability history comment
-merge_request:
-author:
-type: security

ee/changelogs/unreleased/security-conf-epic-visibility.yml

----
-title: Fix displaying epics visibility in issue sidebar
-merge_request:
-author:
-type: security