http://www.computerworld.com/article/3015995/security/grub2-bootloader-flaw-leaves-locked-down-linux-computers-at-risk.html [computerworld.com]

Grub2 bootloader flaw leaves locked-down Linux computers at risk

Pressing the backspace key 28 times can bypass the Grub2 bootloader's password protection and allow a hacker to install malware on a locked-down Linux system.

This bug is being patched in most distros. Apparently not something most need to worry about unless you commonly leave your Linux machine physically available to attackers.