CoreMedia Playback in Apple Mac OS X before 10.8.4 does not properly initialize memory during the processing of text tracks, which allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted movie file.
http://support.apple.com/kb/HT6001
http://support.apple.com/kb/HT5784
http://lists.apple.com/archives/security-announce/2013/Oct/msg00009.html
http://lists.apple.com/archives/security-announce/2013/Jun/msg00000.html