This indicates an attack attempt to exploit a Buffer Overflow vulnerability in Apple QuickTime.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when handling crafted MIME type information. An attacker can exploit this by tricking an unsuspecting user into visiting a malicious webpage and execute arbitrary code within the context of the application.
Apple Computer Quicktime prior to 7.7.3
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.