Configuring preferences and options in Outlook.com
Yes, I completely believe you did NOT subscribe.
That is what Diane and I are trying to say.
On Microsoft's back end, they likely have a function whose sole purpose is to scour every email that comes to you (ideally only the ones NOT going directly to junk).
When that function finds the word "unsubscribe" or something like it along with a link in the email, then the function automatically puts that email address in Subscriptions under Settings, along with the option to "unsubscribe" (as well as Block), which I suspected merely opens the same link that you would have clicked in such an email.
That is why we both are saying do NOT click on any kind of unsubscribe for any spam.
I'm glad you already know not to click on unsubscribe.
You ought to be fine clicking "Block" if you want to remove the entry in Subscriptions, but all it does from what I can tell (from my testing) is hide the entry from Subscriptions and add the entry in "Blocked senders".
So either way, you're stuck with some entry which is still unacceptable.
But to say it is a hacker or a virus is completely wrong. We didn't get hacked and it's unlikely Microsoft did either. It's much more likely someone just screwed up with an update for the filter system which they supposedly eventually got around to fixing.