chfn 1:4.8.1-1ubuntu8.1 1:4.8.1-1ubuntu5.20.04.1 # change users gecos field / name (long over 1024 character /etc/passwd line makes this command's function always return NULL and fail, suid 0)
chfn 1:4.8.1-1ubuntu8.1 1:4.8.1-1ubuntu5.20.04.1 # change a users shell (long over 1024 character /etc/passwd line makes this command's function always return NULL and fail, suid 0)
userdel 1:4.8.1-1ubuntu8.1 # remove a user from the system (blocks this, even as root)