Name: Joshua Melbourne, Victoria, Australia (Zone 10a) Köppen Climate Zone Cfb
I've seen it a couple of times in Firefox in the last day or so. Haven't looked at it closely yet to work out what is causing it (even then I can only make comments to Dave or Jon, as I cannot make those types of changes).
That is the reCaptcha symbol, but it shouldn't be there as we don't use it on the site. My theory is that it is stuck there from another site. I would try restarting Chrome, and then maybe even restarting your phone and it will probably go away.
Jon, I'm getting it with Firefox on iPad and Safari on iPod. When I clicked on it this morning on the iPod it went to a page about Google privacy settings. When I click on it now on the iPad it doesn't do anything, just sits there. I haven't seen it on any other site but NGA.