Microsoft is investigating public reports of a vulnerability in all supported versions of Internet Explorer. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability in Internet Explorer 8 and Internet Explorer 9. Applying the Microsoft Fix it solution, "CVE-2013-3893 MSHTML Shim Workaround," prevents the exploitation of this issue.

Read more: http://technet.microsoft.com/en-us/security/advisory/2887505