Linux UI highlights when dragging the editor window

Buttons and other UI elements of the Linux editor are highlighted when they are over the pointer's original click position.

1. Open UE4Editor
2. Open any project
3. Click on the Maximize button in the top right corner of the editor to set the window to Windowed mode
4. Left click and hold the top bar of the editor window
5. Drag the editor window upwards on the screen

RESULT:
The buttons and other UI elements are highlighted when they are dragged over the mouse pointer's original click + hold position.