DM request issue

I usually have the setting on where i have to accept a message request before we can talk. But today i woke up and saw a random account in my dms. And when i checked it it said that they qccepted my shared feed request,and after that one it said i accepted theirs. It also showed that this happened 3 hours before i opened the app,and i was asleep at that time. Keep in mind i have ZERO history with this person. Not a single message before the ones i just mentioned. The account also seemed to be a scam account but it only had 1 video with a few followers. I checked my login and account history wnd everything seemed to be fine,so it couldn't have been someone logging into my account and accepting it. I just want to know why this happened. Did this evee happen to anyone before? I still find the shared feed thing weird and i wanna know how they suddenly got into my dms like that