Windows 10 Odd square in top left of both screens

[conrad9900]

I have this odd square in the top left of my monitors:



I have changed the PC, the GPU and the monitors but it still shows.

 

[nmsuk]

Must be something you have installed.

 

[bochane]

Looks like a reference to https://www.quantcast.com/about-us/
Does the startup list in the task manager (Ctrl - Alt - Del) show any clue?