Excel logged into strange account

I have a Office 365 family subscription, which I may sometimes use my Office 365 apps for work.

Long story short, on my personal computer, I only logged into my personal account. However, just a few minutes ago, when I opened up Excel app on my computer, I saw that it was logged into this account:

powfuwuwa1@hotmail.com

I don't recall sharing my computer with anyone else, especially for using Microsoft 365 apps. Does this mean my personal account is compromised? Or is it possibly caused by some virus on my computer?