In an unprecedented move, Microsoft Corp. has issued a security advisory to nudge Windows users into applying a critical security update for Macromedia Inc.s ubiquitous Flash Player.
It is the first time the software giant has used its security advisories program to warn about potential problems in a third-party product.
Microsofts advisory comes just days after Macromedia released Flash Player 8 to squash a code execution bug that could be exploited my malicious hackers to take complete control of an unpatched machine.
The Redmond, Wash., software maker noted that the vulnerable Flash Player is redistributed with Microsoft Windows XP Service Pack 1, Windows XP Service Pack 2, Windows 98, Windows 98 SE and Windows Millennium Edition.
The company urged all Windows users to upgrade to follow Macromedias instructions for upgrading to the patched versions of the Flash Player.
"If customers are not using Macromedia Flash Player on their system, or customers do not need Macromedia Flash Player, they can disable the ActiveX control in Internet Explorer to help protect against these vulnerabilities," Microsoft said.
The company also suggested a list of workarounds to help block known attack vectors, including instructions for temporarily preventing the Macromedia Flash Player ActiveX control from running in Internet Explorer.
Among Microsofts workarounds is a recommendation that users completely remove the Flash Player or un-register the Macromedia Flash Player ActiveX control.
The recommendations are all aimed at protecting Windows users from a Flash Player vulnerability that was privately reported to Macromedia four months ago.
The flaw was flagged in Macromedia Flash Player 188.8.131.52 and earlier versions.
According to eEye Digital Security, the private research firm that reported the issue to Macromedia, the bug affects Macromedia Flash 6 (on all Windows platforms) and Macromedia Flash 7 (on all Windows platforms).
eEye said the vulnerability opens the door for a malicious hacker to run arbitrary code in the context of the logged-in user. "An array boundary condition may be violated by a malicious .SWF file in order to redirect execution into attacker-supplied data," the company said.
The .SWF (Small Web Format) extension is used to play Flash "movies" over the Internet.
eEye said the vulnerable code exists in Flash.ocx, which embodies the code responsible for playing back .SWF files. "One function maintains a large, 256-element table of function pointers on the stack, and uses a frame-type identifier read from the SWF file as an index into the array, without enforcing the array boundaries."
"Reliable exploitation using this technique within [Microsoft Corp.s] Internet Explorer has been demonstrated," eEyes alert said.
Macromedia has posted fixes to its Download Center.
Windows users can use this Web page to determine which version of the Flash player they have installed.