Brave stopped Meerkat app working

When I tried to log in to my Meerkat app on my android phone, it went to my default Brave browser but no website would open. Then I got a small grey box on my screen with “comparethemarket.com” on it. I could move it around the
screen but couldn’t get rid of it. Had to resort to rebooting the phone. Then I used Firefox instead which worked perfectly. What’s going on please ?