Security researchers have discovered new security risks affecting media players from Apple and Microsoft.

On Tuesday Apple released a patch for a vulnerability in iTunes on the Mac OS X and Windows platforms, that could allow attacks via malicious playlists. On Monday anti-virus firm Panda Software warned that two new "Trojan horse" exploits have surfaced in the wild, infecting Windows users via the new digital rights management (DRM) functionality in Windows Media Player (WMP) 10.

The iTunes vulnerability is caused by a bug in the way the software handles "m3u" and "pls" playlist files. A malicious playlist file could crash the software and run exploit code on the user's system, according to Apple. Mac OS X, Windows XP and Windows 2000 are affected. Version 4.7.1 fixes the problem, and is available from Apple's Web site.

ITunes is the only desktop software that works with Apple's popular iPod music player, and is widely used on both Windows and Mac desktops, making it a potential threat to enterprise IT systems.

PandaLabs said it has discovered two Trojans in the wild, called Trj/WmvDownloader.A and Trj/WmvDownloader.B, designed to download a variety of spyware and adware onto users' systems.

Ironically, the Trojans make use of anti-piracy features added to Windows with Windows XP Service Pack 2 and WMP 10, according to Panda.

When WMP 10 attempts to play media files protected by a licence that isn't found on the PC, it searches for a licence on the Internet. The two Trojans masquerade as a licence-protected video file, but instead of downloading a licence, they download and install a list of more than a dozen spyware and adware programs onto the user's PC.

"The video files infected by these Trojans have a .wmv extension and are protected by licenses, supposedly issued by the companies overpeer (for Trj/WmvDownloader.A), or protectedmedia (for Trj/WmvDownloader.B)," said Panda in an advisory."If the user runs a video file that is infected by one of these Trojans, they pretend to download the corresponding license from certain Web pages." A single infection can add hundreds of files and thousands of registry entries to a user's computer, Panda said.

The Trojans have been detected in a video files with a wide variety of names on peer-to-peer networks such as Kazaa and eMule, but can also be distributed via e-mail attachments, FTP or Web downloads or by other means, the company said. Users can protect themselves with up-to-date antivirus software.