Microsoft secure boot has been comprimised by the discovery of a Private Key that allows it to be bypassed.
The risk this vulnerability introduces can be mitigated by locking down your BIOS and boot sequence. Call Sierra for more information.
"Microsoft has inadvertently demonstrated the intrinsic security problem of including a universal backdoor in its software after it accidentally leaked its so-called "golden key"—which allows users to unlock any device that's supposedly protected by Secure Boot, such as phones and tablets.
The key basically allows anyone to bypass the provisions Microsoft has put in place ostensibly to prevent malicious versions of Windows from being installed, on any device running Windows 8.1 and upwards with Secure Boot enabled.
And while this means that enterprising users will be able to install any operating system—Linux, for instance—on their Windows tablet, it also allows bad actors with physical access to a machine to install bootkits and rootkits at deep levels. Worse, according to the security researchers who found the keys, this is a decision Microsoft may be unable to reverse."
Read more on ArsTechnia's security blog: http://arstechnica.com/security/2016/08/microsoft-secure-boot-firmware-snafu-leaks-golden-key/