Hi!
I think this is a XSS in MS SharePoint, you can reproduce it in SharePoint test server using for example following url:

http://www.example.com/sharepoint/default.aspx/%22);}if(true){alert(%22qwertytis

This is due a lack of string stripping when putting the path into javascript.
 
It seems to work at least on every main page.
 
I tried to check for this in the web, but I didn't found this hole anywhere.
 
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Regards,
Solarius - http://www.solarius.name