Microsoft has released a new update for both Windows 8 and Windows Server 2012

This cumulative update includes the following performance and reliability improvements:

Enable enterprise customers to customize the default lock screen.
Improves the performance when you wake the computer and when the computer is asleep, in order to improve battery life
Resolves an issue that may prevent Windows Store Apps from being installed fully
Other software updates and performance improvements

Update for Windows 8 (KB2758246)
Update for Windows 8 for x64-based Systems (KB2758246)
Update for Windows Server 2012 (KB2758246)