Black Box Around Active Item

My bluetooth mouse ran out of battery and I was trying to do some keyboard only navigation. Somehow I turned on an option that places a totally annoying black box or rectangle around whatever item is active and has focus. This could be an icon in the finder or text in a warning box.

I tried to take a screenshot for clarity, but the act of taking the screenshot seems to move the box before the shot is taken.

Any idea how I can undo this?!? I'm thinking it's a Universal Access...

Black Box Around Active Item