Hey TFA, other people have gone to prison for finding monotonic user/account IDs and _testing_ their hunch to see if it's true. See, doing that puts you at great risk of violating the CFAA. Basically, the moment you knew they were allocating account IDs monotonically and with a default password was the moment you had a vulnerability that you could report without fear of prosecution, but the moment you tested that vul…
Would a better course of action here have been for him to generate a “test test” account under his?
This happens over and over again because for so many companies their natural thing is to hid any problem and threaten to sue anyone who discloses. Software problems have broken that typical behavior, to some extent.
I salute the author of this post who dared to do the right thing. I hope the company comes to their senses and doesn't try to punish the diving instructor. Over and over companies have tried this same "attack the problem reporter" strategy when software problems are revealed.