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Microsoft: Don't press F1 key in Windows XP

Microsoft told Windows XP users today not to press the F1 key when prompted by a Web site, as part of its reaction to an unpatched vulnerability that hackers could exploit to hijack PCs running Internet Explorer (IE).

In a security advisory issued late Monday, Microsoft confirmed the unpatched bug in VBScript that Polish researcher Maurycy Prodeus had revealed Friday, offered more information on the flaw and provided some advice on how to protect PCs until a patch shipped.

"The vulnerability exists in the way that VBScript interacts with Windows Help files when using Internet Explorer," read the advisory. "If a malicious Web site displayed a specially crafted dialog box and a user pressed the F1 key, arbitrary code could be executed in the security context of the currently logged-on user."

Last week, Prodeus called the bug a "logic flaw," and said attackers could exploit it by feeding users malicious code disguised as a Windows help file -- such files have a ".hlp" extension -- then convincing them to press the F1 key when a pop-up appeared. He rated the vulnerability as "medium" because of the required user interaction.

Windows 2000, Windows XP and Windows Server 2003 are impacted by the bug, said Microsoft, and any supported versions of Internet Explorer (IE) on those operating systems -- including IE6 on Windows XP -- could be leveraged by attackers. Previously, Prodeus had said that users running IE7 and IE8 were at risk, but had not called out IE6.

Until a patch is ready, users can protect themselves by not pressing the F1 key if a Web site tells them to, said Microsoft.



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