A Joomla! 3.6.4 release containing a security fix will be published on Tuesday 25th October at approximately 14:00 UTC.
The Joomla! Security Strike Team (JSST) has been informed of a critical security issue in the Joomla! core.
Since this is a very important security fix, please be prepared to update your Joomla! installations next Tuesday.
Until the release is out, please understand that we cannot provide any further information....