Apple has issued an important security update for its QuickTime multimedia plug-in.

QuickTime 7.5 includes fixes for five flaws in the Windows XP and Vista versions of the tool, four of which also affect the Mac OS version.

All five vulnerabilities could allow an attacker to remotely execute malicious code on a user's system.

Among the vulnerabilities is a flaw in the PICT component within QuickTime. An attacker could use a specially-crafted image file to cause a memory overflow that would allow for remote code execution. The flaw does not affect Mac OS users.

Each of the four remaining vulnerabilities affect Mac and Windows versions. They include issues in the way QuickTime handles Indeo and AAC files, as well as a second vulnerability in the handling of PICT image files.

The fourth vulnerability concerns a flaw in the handling of URLs within QuickTime Player. An attacker could install and run malicious code when the user launches a specially-crafted QuickTime file.

Apple has fixed the vulnerability by forcing the files to be downloaded to Windows Explorer or the Mac OS desktop rather than automatically launched by QuickTime.

Users can obtain the update automatically through the Software Update component or manually through the Apple Downloads website.