Official information about this update is available here:
http://support.microsoft.com/kb/2734608
This update to WSUS 3.0 SP2 is very significant in that it adds operating system patching support for Windows 8 and Windows Server 2012 WSUS clients. In addition, it also fixes minor issues with KB2720211 (which is included in this update). For stand-alone WSUS environments this update also includes the updated version of the Windows Update Agent (WUA): 7.6.7600.256 which addresses security vulnerabilities of the Windows Update client component.
When KB2734608 is installed and you are leveraging the WSUS server engine as a Software Update Point in Configuration Manager, you may notice that when the new catalog is downloaded, the changes in that catalog structure may trigger some unexpected changes in the existing patch management database. Some existing patches may show as Invalid and may require to be re-download and re-distributed throughout the Configuration Manager hierarchy. It is highly likely that some enterprise administrators may not desire this.
A Hotfix to the Rescue!
To prevent these actions from occurring, Microsoft released the hotfix (KB2783466.) This hotfix has to be applied to all Configuration Manager SUP/WSUS systems after the KB2734608 is applied and before the next Patch Tuesday cycle (December 11th, 2012). This hotfix prevents the unnecessary re-downloading and re-distribution of existing patches. Official information about the hotfix can be found here:
http://support.microsoft.com/kb/2783466
Information Regarding the Updated Windows Update Agent
As described above, the KB2734608 update includes a new version of the Windows Update Agent. On standard WSUS systems, they will push out the new updated Windows Update Agent automatically to clients once the KB2734608 is installed. However, for Configuration Manager 2007 systems, the Windows Update Agent is not leveraged in the same way as standalone WSUS systems; therefore the update does not occur automatically. The security issue addressed by the Windows Update Agent update does not impact Configuration Manager, as Configuration Manager does not download their content through the Windows Update Agent. It only leverages the WU APIs for scanning and installation. The update binaries delivered through the Configuration Manager Software Update component are delivered directly from the distribution point, not through a WUA call to WU/MU or WSUS for content. There is no vulnerability exposure here for Configuration Manager Software Update Management clients, thus no need to update the Windows Update Agent to this version.
However if customers would like to upgrade WUA to the latest revision it is recommended to create software distribution command line only package from Configuration Manager using the following command to initiate update process:
wuauclt /detectnow
This package will have to be applied to all managed systems.