To understand the transition from legacy BIOS to UEFI firmware, it’s best to begin with a review of a decades-old system—the 1983 IBM-compatible PC—and continue with a study of its successor ...
Two different vulnerabilities in various UEFI BIOS versions from several providers allow the SecureBoot mechanism to be bypassed. Attackers can even replace the firmware in UEFI BIOSes from Insyde.