Wow! That's spooky. Or maybe it is "spooks" trying to spy on you (not to put too paranoid a twist on it). I would leave it unplugged and locked away somewhere separate from your house. Maybe whoever plugged it in will come asking for it. You should install/change the dead-bolt locks on your doors.
You are right about the Chinese website: no information there about how to use it, just the suggestion it can be used to charge a Li-ion battery. I don't usually waste my time buying undocumented Chinese junk. Most of it appears to be excess inventory from a production run for an OEM. OEM asks for a zillion parts but only accepts a half-zillion or so and declares bankruptcy. Producer of parts is left holding the bag on the unsold inventory, so they market it on eBay or where ever, making whatever claims the public will buy into.