Microsoft originally released this back in June, but pulled it because of a few issues. These have been corrected and it's back!

You should apply this update to the TFS application server, build machines, proxies, and TFS SharePoint portal servers (if you have a multi-tier dpeloyment). Pretty much anywhere the TFS SKU has been installed. SP1 is a pre-requisite and is not included.
Download from http://www.microsoft.com/download/en/details.aspx?id=26211
Details about the update: http://support.microsoft.com/kb/2536929