IPhone7 didn't escape. I was typing while chatting on WeChat, and suddenly a full-screen advertisement appeared (pictured). What happened? Is it poisonous?

Let me ask Apple Customer Service for you. Apple's customer service said that it may be what website you visited recently, and they can push advertisements. Here comes the point! Solution: Settings, Privacy, bottom advertisement, click Restore Advertisement Identifier, and turn on restricted advertisement tracking. So the advertisement will say goodbye! ! ! !