Guidance on Internet Explorer XSS Filter.
The XSS Filter related Blackhat EU presentation discussed a vulnerability that was previously disclosed and addressed in the January security update to Internet Explorer (MS10-002). This attack scenario involved modified HTTP responses, enabling XSS on sites that would not otherwise be vulnerable.
An additional update tothe IE XSS Filteris currently scheduled for release in June. This change will address a SCRIPT tag attack scenario described in the Blackhat EU presentation. This issue manifests when malicious script can “break out” from within a construct that is already within an existing script block. While the issue identified and addressed in MS10-002 was identified to exist on high-profile web sites, thus far real-world examples of the SCRIPT tag neutering attack scenario have been hard to come by.
Source - The Microsoft Security Response Center (MSRC) : Guidance on Internet Explorer XSS Filter