In a security advisory posted on its support site, Microsoft admitted that an ActiveX control -- WebViewFolderIcon, also called "Web View" -- exposes a vulnerability in the Windows Shell that can be exploited by attackers to hijack PCs. The likely attack vector, said Microsoft, would be the now-standard malicious Web site; victims would have to be drawn to the site with e-mailed or IMed lures, or surf to it on their own to be attacked. All currently-support editions of Windows are at risk, including Windows 2000, XP (SP1 and SP2), and Windows Server.
Thursday, security vendors and organizations, including Symantec and US-CERT, warned that exploit code had been released. The bug was originally reported in July as part of HD Moore's "Month of Browser Bugs" project where he identified dozens of flaws in IE and other Web browsers. The vast majority of those vulnerabilities remain unpatched.
Microsoft also detailed several workarounds that users could implement until a patch is available, including disabling all ActiveX controls and setting the "kill bit" to turn off only the WebViewFolderIcon control. The latter, however, requires editing the Windows Registry, which can be hazardous if done incorrectly.
The advisory can be found here.