Microsoft is investigating public reports of a vulnerability in Internet Explorer 6, Internet Explorer 7, Internet Explorer 8, and Internet Explorer 9. Internet Explorer 10 is not affected. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability.
http://technet.microsoft.com/en-us/secu ... ry/2757760
http://www.reuters.com/article/2012/09/18/net-us-microsoft-browser-idUSBRE88G1CA20120918
Do take the necessary precautions of using an alternative browser until the risk is taken care of.