Next time anyone gets redirected to that spam page, I want you to copy the url of that page and post it here. Also, let me know what kind of mobile device you were on when it happened.
To explain what's happening, we get our ads from several Ad Services who have a wide variety of ad types available. We choose the ad types we want and the service puts them in place, but that part is entirely done by bots, who choose the ads based off things like cookies, guesses at the users demographic, geographic location, etc. Sometimes the bots choose the wrong ad type and serve it up to you (they aren't super smart bots), and when that happens we put a block in place to stop that ad from being served again. Get me the link, and I can put that block in place