I’m a fan of this post by @aaronpk covering the topic. Made it easy for me to understand the problem.
https://aaronparecki.com/2020/05/31/30/the-real-cause-of-the-sign-in-with-apple-zero-day
https://aaronparecki.com/2020/05/31/30/the-real-cause-of-the-sign-in-with-apple-zero-day
