Windows Store app has received a new update for both Windows 10 PC and Windows 10 mobile. The latest update version is 11705.1000.78.0. The latest update is important one which brings elements of fluent design.
Windows Store Changelog:
The latest update brings some fluent design elements related UI changes.
Also it gets background blur effect
Bug fixes and performance improvements.
Rightnow this effect is only visible on Windows 10.