It seems that Windows 8.1 will come with the ability to automatically update apps in Windows Store in the background. In the current Windows 8, user has to go to Windows Store and update the apps, but enabling auto-updates will further simplify the user experience. Google Android OS already has this similar feature where user can give permission for an app to automatically update when it is available. Recently, the Movie Moments app in Windows 8.1 build got updated automatically without user’s consent.
Here is the observation from winbeta,
After further investigation, in the Windows Update “installation history,” it shows “Installation Successful: Windows successfully installed the following update: Microsoft.MovieMoments.”
Not only was that the only app that was updated, but apps by the names of “PlayReady Client”, “VCLibs Preview Internal” and “WinJS 2.0 Preview Internal” are also updated, and have version numbers ranging from 6.3.9345 to 6.3.9391.
Source: Winbeta via: BetaArchive