Thx, NW; it is definitely google ads. A pile of people are reporting the same issues:
https://productforums.google.com/for...se/szfNNkPrkLI
https://productforums.google.com/for...se/3q1wwM-j7Cg
Google is working to weed out the crap, and I added these domains to our own block list. It's a bit like whackamole, as if Google lets the schmoes through, there can always be more, but it happens pretty rarely as they are generally on top of things. Sorry for the trouble, and for the short term if you do disable ads in your control panel the problem shouldn't re-occur, at least on this site.