docs: Add a release note for CVE-2019-13122

Signed-off-by: Daniel Axtens <dja@axtens.net>
(cherry picked from commit f48179f)
Signed-off-by: Daniel Axtens <dja@axtens.net>

Author: daxtens

releasenotes/notes/CVE-2019-13122-e9c63aa346ed15c2.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    CVE-2019-13122 has been fixed. Andrew Donnellan discovered an XSS
+    via the message-id field. A malicious user could send a patch with
+    a message ID that included a script tag. Because of the quirks of
+    the email RFCs, such a message ID can survive being sent through
+    many mail systems, including Gmail, and be parsed and stored by
+    Patchwork. When a user viewed a patch detail page for the patch
+    with this message id, the script would be run. This is fixed by
+    properly escaping the field before it is rendered.