This indicates an attack attempt against a Buffer Overflow vulnerability in Apple iTunes.
The vulnerability is caused by an error when the vulnerable software handles a malicious "PLS" file. It allows a remote attacker to execute arbitrary code by sending a crafted "PLS" file.
Apple iTunes before 9.0.1
System Compromise: Remote attackers can gain control of vulnerable systems.
Upgrade to the latest version of Apple iTunes, 9.0.1 or later.