“Unknown” devices joining home network

Today I’ve gotten about 20 emails (starting around 5am) saying that a new device has joined my home network. All attributes (name, brand, type, model, OS) are given as “unknown”. When I look in the Xfinity app, nothing new is showing up in the list of devices. However, the notifications are also showing up in the My Account app’s Recent Activity list. Suffice it to say I have not newly connected a bunch of devices in the middle of the night or throughout the rest of the day. Does anyone know what is going on?