Joomla! 3.4.5 is now available. This is a security release for the 3.x series of Joomla which addresses a critical security vulnerability. We strongly recommend that you update your sites immediately. This release only contains the security fixes; no other changes have been made compared to the Joomla 3.4.4 release.

What’s in 3.4.5

Version 3.4.5 is released to address three reported security vulnerabilities and includes additional security hardening of the UploadShield system.
Security Issues Fixed

High Priority – Core – SQL Injection (affecting Joomla 3.2 through 3.4.4) More information » http://developer.joomla.org/security-centre/628-20151001-core-sql-injection.html
Medium Priority – Core – ACL Violations (affecting Joomla 3.2 through 3.4.4) More information » http://developer.joomla.org/security-centre/629-20151002-core-acl-violations.html
Medium Priority – Core – ACL Violations (affecting Joomla 3.0 through 3.4.4) More information » http://developer.joomla.org/security-centre/630-20151003-core-acl-violations.html

https://www.joomla.org/announcements.html