So this does sound like it’s definitely something on the site. I know if you search to ask things such as about the  appearing, it comes up with a lot of varying topics.
But as much as I can see this, I’m not anywhere near knowledgeable enough to know what to guide to afterward.
Also to circle back around, you’re saying this issue doesn’t happen in any of the others except for Brave? If so, I really do hope you could give it a test on Chrome or Chromium. By all means can uninstall after, but wondering if it’s just a chromium engine issue.