Microsoft is investigating reports of a new vulnerability in Internet Explorer that could enable an attacker to run arbitrary code on a victim's machine if he or she is persuaded to visit a malicious website and press the "F1" key in response to a pop-up dialog box. The flaw, however, does not affect newer versions of the operating system: Windows 7, Vista and Server 2008, according to a post Sunday on the Microsoft Security Response Center blog. The bug, which involves the use of the VBScript language and Windows Help files, was revealed Friday by security firm iSEC. There have been no known attacks, Microsoft said. -- DK