In the reproduction project, the cursor is being set to a custom cursor which is defined as a blank image in the resource file for the project using WSA.Cursor.SetCustomCursor()

To reproduce:
1) Open the attached project
2) Switch platform to UWP and Build type to XAML
3) Make a build of "main" scene, deploy it and run on PC
4) Move the mouse a bit
Result: Default system cursor appears

NOTE: you can see expected behavior by running the same XAML build on PC built with pre-2017.3.0b3 Unity versions
2017.3.0b4 has a bit different behavior as it changes the cursor at first but as soon as you click left mouse button it reverts back to the default cursor

Reproduced on: 2017.3.0b4, 2017.3.0b3
Regression introduced with 2017.3.0b3
Not reproducible on: 2017.2.0f3, 2017.1.2p1