Does ME Manufacturing mode allow the user to change all the configuration? Does it mean that hackers who incidentally purchased such a machine (but probably not Apple's) with ME Manufacturing mode enabled, can theoretically port coreboot to the machine, then flash their own public key fingerprints into ME, using Boot Guard to protect firmware signed by themselves instead of OEM's?
I remember several bunches of Lenovo laptop series released a few years ago seems to have the same vulnerability, and porting coreboot to those computers with earlier chipsets is a real possibility, only prevented by Boot Guard signature. But finding these unpatched and vulnerable series of machines is a hit-or-miss game with minimum chance of success. If someone really implements tools to do all these things, is it possible that the secondhand vulnerable motherboards would be the gold in the hacker communities and be sold at a high price?
Another fact is that ME is a part of the PCH, which is located on the CPU package. If a hacker has access to a BGA rework technician in a professional repair workshop, it should be possible to desolder the original CPU from the board, and install a new one with unconfigurated ME to "own" the machine.
I remember several bunches of Lenovo laptop series released a few years ago seems to have the same vulnerability, and porting coreboot to those computers with earlier chipsets is a real possibility, only prevented by Boot Guard signature. But finding these unpatched and vulnerable series of machines is a hit-or-miss game with minimum chance of success. If someone really implements tools to do all these things, is it possible that the secondhand vulnerable motherboards would be the gold in the hacker communities and be sold at a high price?
Another fact is that ME is a part of the PCH, which is located on the CPU package. If a hacker has access to a BGA rework technician in a professional repair workshop, it should be possible to desolder the original CPU from the board, and install a new one with unconfigurated ME to "own" the machine.