Unauthorized Windows Machine Added to My iCloud

I woke up this morning to an alert that a windows machine had been added to my iCloud account. I do not recognize the machine and have checked my desktops in the house.

I did not get an alert on my multi factor to let me know that this device was added. I have changed my password and signed out all machines.

Does anyone know how this got added without me authorizing it through multifactor? Do I need to do anything besides changing my password and signing out all devices?

I did get an update to 18.1 last night if that matters.

Any help would be appreciated.