Random black text box appeared on Safari

I’m not sure if this is an iPhone specific issue or something broader but a few weeks ago I was on Safari and at the bottom left of the Google page I noticed a strange empty black text box. I clicked on it and was able to type in it, but nothing else happened, even after clicking return. I’ve done some searching and haven’t been able to find anybody talking about the same box, it always shows results about hover typing, which this doesn’t appear to be. Any idea what this could be? (not the 3 out spots that I marked up in photos, the larger box at the bottom left above “Visit”.)