Microsoft has recently released an update to the Microsoft update/Windows update client with security enhancements. It also include further hardening of infrastructure used by WU/MU client and a more secure communication channel between WU/MU Client and Service. You can read more about the changes in WU/MU at KB 2887535.
The update is applicable to Windows 7 Service Pack 1, Windows Server 2008 R2 Service Pack 1, Windows 8, Windows RT, Windows Server 2012 and the rollout will begin today. Similar to past updates, this update will be automatically installed if Automatic Updates is turned ON, either set to automatically install updates or notify to download/install updates.
As with past updates, this update will not change your current Windows Update or Automatic Updates settings. Anytime Windows Update (or Automatic Updates) is turned ON, either set to automatically install updates or notify to download/install updates, Windows Update will take care of updating itself.
Read more at Microsoft.