Ever since I upgraded to macOS High Sierra, I’ve had a black rectangle on my screen:
My cursor started out inside it, and when I try to move my cursor outside of it, it follows my cursor:
I’ve tried restarting and quitting all of my other apps, it still shows up.
If I switch the “Zoom style” in System preferences → Accessibility → Zoom to “Picture-in-picture,” the box still shows up, but it stops following my cursor.
How can I get rid of this annoying box?