Why does my macbook suddenly have Other as an user account?

Why does my macbook suddenly have Other as an user account when I did not authorize such thing nor do I have guest account enabled?

It does not show up in the list of user accounts nor the top-right drop-down menu when you click on your username. Therefore I cannot delete/remove it.

My wife has had Find My Mac enabled for weeks and this has suddenly appeared today. She and I have been and are still both administrators with our own passwords to login into our accounts.

I have had all the location services on my end off and are still. I don't know about her end except that she has Find My Mac on, and has been like that for weeks without problem.

FileVault and Firewall were already on and still are.

"Allow apps downloaded from: App Store and identified developers" was on instead of just "App Store" so I just changed that but the problem is still here.

We have had this computer since June/July.

I already had Two-Factor Authentication on for my iCloud.

I had Power Nap on and I am turning that off now. (when compared to default settings)

"Prevent Computer from sleeping automatically when the display is off." was On. (when compared to default settings)

"Put hard disks to sleep when possible." was Off. (when compared to default settings)

I reverted my Energy Saver settings to default (where it says to revert to default settings) on both Battery and Power Adaptor.

I changed my Mac password just after I noticed this problem.

It seems to disappear when I restart the macbook and only appear when resuming from Sleep.