GRUB security

Edit file /etc/default/grub :

GRUB_DEFAULT=0
GRUB_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_QUIET_TIMEOUT=true
GRUB_DISTRIBUTOR='Linux'
GRUB_CMDLINE_LINUX_DEFAULT="quiet"
GRUB_CMDLINE_LINUX=""
GRUB_DISABLE_SUBMENU=y
GRUB_DISABLE_RECOVERY=true

For each menu entry, add --unrestricted in /etc/default/10_linux , changes maybe next of lines 132 and 134 :

132:      echo "menuentry '$(echo "$title" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-$version-$type-$boot_device_id' --unrestricted {" | sed "s/^/$submenu_indentation/"
134:      echo "menuentry '$(echo "$os" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-simple-$boot_device_id' --unrestricted {" | sed "s/^/$submenu_indentation/"

[*] - SecureInfo.eu, /System/grub.md

GRUB security