Apple released a new version of iTunes yesterday, and this latest release - version 10.6.3 - contains a single security fix for Macs. According to Apple's release notes:
A heap buffer overflow existed in the handling of .m3u playlists.
Importing a maliciously crafted .m3u playlist may lead to an unexpected application termination or arbitrary code execution.
You can install the new version of iTunes via Software Update, or download it here.