Black box in the center when exporting

i got an image with a small black box flashing on and off.

black box.jpg (381.77 KiB) Viewed 205 times

i find there's a node using window (doing vignette thing), and in the highlight parameter i might touch the mini panel by mistake so it's -0.02, very very tiny so it might be the reason. after I change it to 0, black box is gone.

Is it possible this is Data Burn-in turned on doing something it shouldn't do?

Just go through every node, one at a time, turn each on and off, and see if you can get rid of the strange phantom black square.

Is it possible this is Data Burn-in turned on doing something it shouldn't do?

Just go through every node, one at a time, turn each on and off, and see if you can get rid of the strange phantom black square.

not the data burn in, just the very little number in highlight slider