An adversary has an unknown exploit, and it could be used on a large scale to attack your platform. Your threat isn’t just your adversary, but also anyone who developed or sold the exploit to the adversary. The entire chain of information from conception to final product could be compromised anywhere along the way, and sold to a nation state on the side, blackmailed or bribed out of someone, or just used maliciously by anyone with knowledge or access. How can Apple make this problem go away?
The easiest technical solution is a boot password. The trusted boot chain has been impressively solid for the past several years, since Apple minimized its attack surface after the 24kpwn exploit in the early days. Apple’s trusted boot chain consists of a multi-stage boot loader, with each phase of boot checking the integrity of the next. Having been stripped down, it is now a shell of the hacker’s smorgasbord it used to be. It’s also a very direct and visible execution path for Apple, and so if there ever is an alleged exploit of it, it will be much easier to audit the code and pin down points of vulnerability.