airdrop "contacts only" appears stranger in my receiving network
This is disturbing on so many levels. I was using airdrop to transfer files between my macbook and my iPhone in my apartment. My airdrop is always on "contacts only" and never "everyone". Yesterday I found out that there is someone else's iPad whose name I have never heard of appeared in my airdrop receiving network, but I am definitely sure that he is a total stranger. I even searched my hundreds of contact list shared via iCloud to be sure. But this guy just appears nowhere and won't go away. Knowing that a complete stranger could be sending or receiving my files and maybe somehow get to my data is creepy. Can anyone help to explain this? Or better, is there a way to block certain contact on your "contacts only" network? Thanks!
MacBook Pro (15-inch, Late 2016)