Microsoft on Thursday confirmed that Windows XP and Windows Server 2003 contain an unpatched bug that could be used to infect PCs by duping users into visiting rigged Web sites or opening attack e-mail.

The company said it has seen no active in-the-wild attacks exploiting the vulnerability.

The bug in Windows' Help and Support Center -- a component that lets users access and download Microsoft help files from the Web -- doesn't properly parse the "hcp" protocol handler, Microsoft said in an advisory issued Thursday afternoon. Attackers can leverage the vulnerability by enticing users to malicious or hacked Web sites, or by convincing them to open malformed e-mail messages.

Windows Vista, Windows 7, Windows Server and Windows Server 2008 R2 are not vulnerable to the attack.

Microsoft plans to produce a patch, but has not set a release date. "Microsoft is currently working to develop a security update for Windows to address this vulnerability," the advisory stated. July 13 is Microsoft's next scheduled Patch Tuesday, but it sometimes issues patches outside its monthly plan. The last time it did so was in late March when it fixed a bug in Internet Explorer that attackers were aggressively exploiting.

Full story: Computerworld