Followed a link from Wikipedia in Chrome and got bombarded with all manner of nonsense, including a bald statement that my Mac was infected with three viruses & one item of malware. Did I wish to continue with their recommendation to download & use MacKeeper to fix it all up?
In the absence of a "No, you filthy cunting bastards, I do not" button, I simply quit all internet activity and commenced a scan of the system with Sophos Home. That's 65% done & noting nasty has been found yet.