A Trojan exploiting a flaw in Apple's QuickTime that was patched two weeks ago is infecting MySpace.com users' computers and stealing their passwords.

The attack is reminiscent of one late last year that plagued MySpace users and forced the popular social networking site to shut down hundreds of profiles.

Like that December exploit, the new attack uses QuickTime's "HREF" function, which allows movies to contain URLs or JavaScript that load web pages. Rather than issue a fix to all QuickTime users then, however, Apple took the unusual step of letting MySpace itself link to the blocking code. In other words, only MySpace users were protected.

"This function is not strictly a bug or a vulnerability, but it is something that can be misused," said Ivan MacIntlel, research director at Trend Micro.

An Apple spokesman said that the company patched QuickTime against the flaw in its 5 March security update. New versions for both Mac OS X and Windows were released that day.

But apparently not every QuickTime user has updated to the patched Version 7.1.5. The most recent exploit again uses HREF to embed malicious JavaScript in a QuickTime movie posted on a MySpace page. When a user clicks to play the movie, the JavaScript Trojan - which is hosted on an external site - grabs personal information of the MySpace user.

F-Secure ticked off the pieces the Trojan steals: MySpace username, FriendID, MySpace Display Name and other user passwords. The data is uploaded to a server at the domain Profileawareness.com, which is a members-only forum that "provides working methods of tracking exactly who visited your MySpace profile."

Although MacIntlel could not confirm that the QuickTime update of 5 March would stop the new attack - his research teams are still investigating - he said that it is often true that people don't upgrade vulnerable software. "It's common that people aren't updating right away," he said.

MySpace representatives did not return a call for comment.