Them annoying “you have won” smartphone popups

So there you are, reading an article from a legit source, and this annoying “You have won a $500 Amazon gift card” pops up, and won’t go away.

You run a virus check – nothing, you run a malware check – nothing

So what do you do, when no virus or malware is found? Where are these pop-ups coming from?

Has this happened to you? How did you resolve it?