The released documents are very old, so we don't really know what's the actual state of the art. This is what I did (any express or implied warranty is disclai

The released documents are very old, so we don't really know what's the actual state of the art. This is what I did (any express or implied warranty is disclaimed): > diskutil list /dev/disk0 (internal): #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme xxx.x GB disk0 1: EFI EFI 314.6 MB disk0s1 2: Apple_CoreStorage <Root_Name> xxx.x GB disk0s2 3: Apple_Boot Recovery HD 650.0 MB disk0s3 ... > sudo diskutil mount /dev/disk0s1 Volume EFI on /dev/disk0s1 mounted > ls -R /Volumes/EFI/EFI/APPLE EXTENSIONS FIRMWARE UPDATERS /Volumes/EFI/EFI/APPLE/EXTENSIONS: Firmware.scap /Volumes/EFI/EFI/APPLE/FIRMWARE: MBxx_xxxx_Bxx_LOCKED.fd /Volumes/EFI/EFI/APPLE/UPDATERS: MULTIUPDATER USBCVA ... Be sure there are no unwanted extensions. > shasum -a 256 <MBxx_xxxx_Bxx_LOCKED.fd> A sha hash is returned, check it against https://github.com/gdbinit/firmware_vault https://github.com/gdbinit/firmware_vault. If there's a mismatch, you may be affected.