Buffer overflow in Apple QuickTime 7.5.5 and iTunes 8.0 allows remote attackers to cause a denial of service (browser crash) or possibly execute arbitrary code via a long type attribute in a quicktime tag (1) on a web page or embedded in a (2) .mp4 or (3) .mov file, possibly related to the Check_stack_cookie function and an off-by-one error that leads to a heap-based buffer overflow.