A Joomla 3.4.5 release containing a security fix will be published on Thursday 22nd October at approximately 14:00 UTC. The Joomla security 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 Thursday. Until the release is out, please understand that we cannot provide any further information.