Microsoft published KB article #983438 late yesterday, with details about a XSS vulnerability within a SharePoint site. This vulnerability may be used to elevate privileges in Sharepoint. SharePoint Services 3.0 and SharePoint 2007 are affected.

Microsoft notes that the vulnerability is harder to exploit if Internet Explorer 8's built in XSS filter is used by administrators of the site. Another action that may help to mitigate the problem is to restrict access to the vulnerable Help.aspx file. With SharePoint using "httponly" cookies, the impact of the vulnerability is somewhat limited.

[1] http://www.microsoft.com/technet/security/advisory/983438.mspx
[2] http://blogs.technet.com/srd/archive/2010/04/29/sharepoint-xss-issue.aspx

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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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