I just noticed a weird effect in my browser window. After some investigation I noticed it is in any window I open including folders on any drive.
It is not a theme setting as I have gone through many and it persists.
The image below shows the upper left hand side of an opened folder. The effect is mirrored on the right side and the whole window has a greyed out/dark color to it. See the little F shape? reversed on right side of screen.