Thank you for the explanation! I get your point now, although I have yet to come across a good use case where this would add any value. But this is just my personal perspective, and just on the one point, no point in dwelling on it. Thank you for for sharing the checklist, I will definitely use it to benefit my work!
What if your attacker was authenticated to your site? With sequential id's they could possibly access data that was not theirs. Like viewing someone else's profile because they can guess the ID? Sequential IDs open up a host of authorization issues.
Agree, the same rule really applies if authenticated. If an attacker is authenticated, then they have access to their account, but you still don't want them to be able to enumerate other accounts, users etc.
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