[ci skip] Add changelog entry for #4877
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 2d9ef69..ee66cc0 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -2,6 +2,15 @@
Change Log
##########
+Version 3.1.2
+=============
+
+Release Date: Not Released
+
+- **Security**
+
+ - Fixed a new URL-encoding attack vector in :doc:`Security Library <libraries/security>` method ``xss_clean()`` affecting Firefox.
+
Version 3.1.1
=============