Update CHANGELOG.md for 11.2.6

[ci skip]

CHANGELOG.md

@@ -548,6 +548,17 @@ entry.
 - Creates Vue component for artifacts block on job page.
 
 
+## 11.2.6 (2018-10-26)
+
+### Security (5 changes)
+
+- Escape entity title while autocomplete template rendering to prevent XSS. !2558
+- Fix XSS in merge request source branch name.
+- Redact personal tokens in unsubscribe links.
+- Persist only SHA digest of PersonalAccessToken#token.
+- Prevent SSRF attacks in HipChat integration.
+
+
 ## 11.2.5 (2018-10-05)
 
 ### Security (3 changes)