Q: Why does an unsigned profile which I have never added appear in my iPhone?

This afternoon I was asked to change my passcode in 60 minutes. It's very strange and then I find many people are asked as well, the earliest I have seen is 2 years ago.

I am told that it's very common to receive such demands on supervised/MDM devices. I'm astonished when I check my profile as I'm definitely sure that I don't have any profiles on my phone.

But there is an unsigned profile!!! I remember every profile I have ever added. I am sure this is not added by me.

Does this mean this profile is to let my iPhone automatically connect to a hidden wifi?

I don't usually turn on my wifi except when I need to use airdrop, so this doesn't cause the actual loss. Nevertheless, it still means a big threat to me. How is this profile added to my phone? I don't lend my phone to others and I have a unlock passcode. How can this be installed on my phone without my awareness?!

BTW, I don't know why my Chinese community account is disabled while I only have several posts since register. So I post this problem here. Thanks in advance to anyone who may offer help.