You’re talking about Airdrop, not Airplay, which lets you play video on another device, like an AppleTV or your laptop. It’s screen mirroring, which has been around for a long time.
Airdrop lets you send photos and files from your phone to someone else’s phone and vice versa. To receive the items, you have to accept from the person doing the sending. If you don’t know who that person is, don’t accept. I’m not aware of a security vulnerability from having Airdrop on your phone, unless you are stupid to accept from strangers.
But, that said, I have mine set to receive only from contacts. If I need to get something from someone who is not a friend (can’t remember ever doing that) I would set it to be able to receive from anyone, and then switch it back.
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