Firmware in Macs has evolved significantly over the years, from Macintosh ROM in classic models to Apple’s version of Open Firmware and then to EFI and UEFI. These changes have brought security risks, highlighted by security researchers who demonstrated attacks on BIOS, including the firmware worm Thunderstrike 2. Apple has introduced tools like eficheck to monitor and update firmware, particularly in newer models like those with the T1 and T2 chips, which have dual sets of firmware. The shift to Apple silicon Macs in 2020 has further changed firmware to support Secure Boot, focusing on a verified chain of trust in the boot process.
https://eclecticlight.co/2024/10/26/a-brief-history-of-mac-firmware/