When viewing the list of message templates, one could pass through a variable called selectedChild through the URL which would specify which of the two lists it would default to showing. This variable was not properly validated against the known two types (user and workflow). There is now proper validation on the url parameter
CiviCRM Versions prior to 4.7.26 and 4.6.33
CiviCRM Versions 4.7.26 and 4.6.33
Upgrade to the latest CiviCRM Version:
- 4.7.26
- 4.6.33
or later
If you cannot upgrade apply the following patch
Sean Madsen of Left Join Labs for reporting the issue
Seamus Lee of Australian Greens for fixing the issue