That shouldn't come as a surprise to anyone who has an app on any app store. I get at least two emails per week from some shady advertiser that wants to place ads, add notifications, gather user data or some else equally awful.

I had at least one app where I didn't pay close enough attention to the permissions it required upfront and at some point it started injecting ads into random pages (it was a stopwatch, by the way). I guess the only way to effectively counter this is a better permission system.