Hello Everyone,
I am running kali verision: 4.18.0.-kali2-amd64

Just downloaded a Jpeg image from internet and used it as my desktop background, immediately, I was logged out of the OS and it asked for username and password.

I thought, it might be a malware but, scanned using virus total and no alarms shows up.

Tried to change the wallpaper again back and forth but, this time it did not ask for login.

Any thoughts ?