I'm not sure how helpful it'd be but I had a similar situation that I reported to Mahz awhile back. I was browsing an old RP that had a linked image (according to Mahz) that would hijack my browser and try to divert me to a website that was thankfully stopped by Chrome blocking it.

As I said before, I'm not sure if it can help [@TheUnknowable]'s situation, but I figured information from a similar issue could potentially help figure out what's going on.