Proof-of-concept code that exploits a critical bug in Windows Media Player has gone public, Microsoft Corp. warned users late Thursday.
A vulnerability in Media Player 9 and 10 can be used by attackers to grab control of a PC, security researchers warned. A malicious .asx-formatted playlist, if opened by an unsuspecting user, could completely compromise the machine.
"We're aware of proof-of-concept code published publicly affecting Windows Media ASX file format [and] we are currently investigating," wrote Alexandra Huft, a security program manager with the Microsoft Security Response Center, on the team's blog. "We are not currently aware of attempts to exploit this vulnerability," she added.
Because .asx playlists open automatically within a browser, hackers would only need to coax users to a malicious Web site to snatch their systems. Microsoft has offered no workarounds or other tactical advice.
The Media Player vulnerability was first reported Nov. 22 by eEye Digital Security, which originally listed it as only a denial-of-service risk. Other security vendors, including Internet Security Systems Inc. and FrSIRT, posted warnings Thursday.
FrSIRT, which labeled the vulnerability as "critical," advised Windows XP users to upgrade to Media Player 11, disable the .asx format, or change settings so that playlists don't automatically open within Internet Explorer.
Microsoft plans to release six security updates Tuesday, Dec. 12, five of which will involve Windows. In its usual early notification, however, the Redmond, Wash. developer did not say whether the Media Player bug would be fixed this month.