The same thing just happened to me when a Safari-looking warning popped up with the message “your OS has crashed due to a 3rd party issue, please call 1 866 537 7060…”
Thinking it suspicious but since my Safari was frozen (though not the rest of my Mac), I used my iPad to look up 1 866 537 7060 and came to this thread.
Alas I couldn’t clear Safari’s cookies & website data because it was frozen, so I force quit it.
When I relaunched it, I cleared the cookies & website data.
But I’d like to know what causes this issue, and how I may prevent it from happening again.