User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists in the QuickTimeAudioSupport.qtx library when parsing malformed QDMC and QDM2 codec atoms. By modifying specific values within the stream an attacker can cause heap corruption which can lead to arbitrary code execution under the context of the currently logged in user.
Patch Availability:
Apple has issued an update to correct this vulnerability. More details can be found at: http://support.apple.com/kb/HT4077