It sounds like unsigned Option ROMs are an even bigger problem. If anything, UEFI provides an effective defense via Secure Boot. Sadly, Apple doesn't currently

It sounds like unsigned Option ROMs are an even bigger problem. If anything, UEFI provides an effective defense via Secure Boot. Sadly, Apple doesn't currently implement this feature -- at a minimum, they'd need to upgrade from EFI 1.10 to UEFI 2.3 to even be able to consider it.