‘Other..’ account at login screen in OS X El Capitan

Hello,

I have a question regarding the new account which has been suddenly automatically created on my login window.

When i opened my computer i came across a new user account called 'Others..' and it replaced my Guest account. When I pressed it, it came with two text fields requesting for username and password.

I have tried to search for this problem and i came across two solutions, and both of them didn't work. Below are the solutions which i have tried

1. Someone suggested that it is because the root account has been enabled, after which i checked and found out that it wasn't enabled. I even tried enabling, disabling and restarting the computer but it but it didn't help
2. Then i came across a website where someone suggested to use the following command in terminal
   sudo defaults write /Library/Preferences/com.apple.loginwindow SHOWOTHERUSERS_MANAGED -bool FALSE
   this command helped to remove the new account but at the same time it hid the guest account. So if i disable or enable the guest account it wont be visible on the login screen.
3. I have also tried checking the new account in System preferences > Users & Groups but i cant find it there either. And this account shows in my login screen regardless if the Guest user is on or off.

Specifications:

MacBook Pro (Retina, 13-inch, Mid 2014)

OS X El Capitan - Version 10.11.2

Thank you very much in advance.

Best regards