Information
Operating systems booted with United Extensible Firmware Interface (UEFI) must require a unique superusers name upon booting into single-user mode and maintenance.
If the system does not require valid authentication before it boots into single-user or maintenance mode, anyone who invokes single-user or maintenance mode is granted privileged access to all files on the system. GRUB 2 is the default boot loader for RHEL 8 operating systems and is designed to require a password to boot into single-user mode or make modifications to the boot menu.
Solution
Configure the system to have a unique name for the grub superusers account.
Edit the /etc/grub.d/01_users file and add or modify the following lines:
set superusers="[someuniquestringhere]"
export superusers
password_pbkdf2 [someuniquestringhere] ${GRUB2_PASSWORD}
Generate a new grub.cfg file with the following command:
# grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg