It would appear that Microsoft Windows 8.1 and Server 2012 R2 are only thirty days away from not receiving security updates, or more precisely from the beginning of patch Tuesday in May 2014 .
Well that is not entirely true, but instances running these operating systems are required to have installed KB2919355 (http://support.microsoft.com/kb/2919355) before the above date to continue to receive security updates.
According to Microsoft, this update was released to simplify servicing across both Windows Server 2012 R2, Windows 8.1 RT and Windows 8.1 and that his update will be considered as a new servicing/support baseline.
The new baseline only exists for Windows 8.1 and Windows Server 2012 R2, so those currently with Windows 8 and Windows Server 2012 operating systems will be unaffected.
For more information on the above:
Happy patching!
Deans Blog 
Microsoft have now re-issued KB291935 addressing the bug which created an encryption mismatch.
Also, Microsoft have extended support for pre-update Windows 8.1 and Server 2012 R2 operating systems until August 2014.
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