Anyone notice a sudden increase in Spam?

I support about 10 tenants with 365 hosted email.  5 of them reported to me in the past week that they are getting inundated with spam going to their inbox (not spam).   I haven't changed anything about their hosted environment but I'm wondering if there was a 365 outlook client update that might have changed things?   I called MS and they said nothing has changed.  I've never had so many end uers from so many different tenants all complain about an increase in spam.

Again, I've changed nothing about their hosted configuration.