Kevin Backhouse discovered that GDM incorrectly launched the initial setup
tool when the accountsservice daemon was not reachable. A local attacker
able to cause accountsservice to crash or stop responding could trick GDM
into launching the initial setup tool and create a privileged user.
The problem can be corrected by updating your system to the following
Ubuntu 20.04 LTS:
Ubuntu 18.04 LTS:
After a standard system update you need to reboot your computer to make
all the necessary changes.