Yesterday, Joomla! 3.6.4 was released, patching a critical privilege escalation and arbitrary account creation vulnerability.
As we’ve seen some exploits attempts occurring in the wild, we feel it is a good time to describe what the issue is and how it was fixed.
Analyzing the Patch
It was fairly easy to figure out where the vulnerable code was, as pretty much all the patch does (with the exception of fixing an additional two factor authentication bug) is basically remove the register method from the UsersControllerUser class.