Apple has fixed a flaw in its QuickTime media playback software that allowed malicious coders to install malware onto vulnerable systems.

The vulnerability - which affects both Windows and Mac OS X PCs - was published as part of the "Month of Apple Bugs" project, which involves a plan to release details of previously undisclosed Mac OS X or Apple application security bugs every day in January.

The QuickTime flaw involves an error in processing malformed Real Time Streaming Protocol (RTSP) URLs. As a result, users tricked into running malformed QuickTime files or who visit a hacker website hosting exploit code are liable to find their systems compromised due to this stack-based buffer overflow bug.

The flaw attracted particular attention because of the availability of exploit code targeting it, which greatly increased the risk it posed.

Apple has released fixes for QuickTime 7.1.3 on Mac OS X v10.3.9, Mac OS X Server v10.3.9, Mac OS X v10.4.8, Mac OS X Server v10.4.8, Windows XP/2000as (explained here), which users are advised to apply in order to guard against exploitation. ®