The company said it was following up public reports of problems relating to a VBScript that is exposed on supported versions of Microsoft Windows 2000, Windows XP, and Windows Server 2003 through the use of Internet Explorer.
"Our investigation has shown that the vulnerability cannot be exploited on Windows 7, Windows Server 2008 R2, Windows Vista, or Windows Server 2008. The main impact of the vulnerability is remote code execution. We are not aware of attacks that try to use the reported vulnerabilities or of customer impact at this time," Microsoft said.
If a malicious website displays a specially crafted dialogue box and the user pressed the F1 key, arbitrary code could be executed, Microsoft warned. On systems running Windows Server 2003, Internet Explorer Enhanced Security Configuration is enabled by default, which helps to mitigate against this issue.