That's definitely some sort of downloaded app doing that. Samsung has nothing in its UI that has the capability of making that appear anywhere. I guarantee you if you restart the phone in safe mode it will be gone which would prove that it's caused by a downloaded app. Press and hold the power button like you're shutting the phone down and when the list of options appears to either restart or shut the phone down, long press on power off and it will give you the option to restart in safe mode. Try that out and see if it disappears, if it disappears you downloaded an app that is glitching out.
