what is the white square on top left of my notification bar?

[AC Question]

I have an LG G4 with T Mobile. Ever since the marshmallow update there is a white square in the top left corner of my notification bar and it won't go away. What is it and how do I get rid of it?

 

[B. Diddy]

Welcome to Android Central! Please see the discussion here: White square in notification bar. Thread closed to prevent parallel discussions.