Reported this exact bug to Zendesk, Apple, and Slack in June 2024, both through HackerOne and by escalating directly to engs or PMs at each company. I doubt we were the first. That is presumably the reason they failed to pay out. The real issue is that non-directory SSO options like Sign in with Apple (SIWA) have been incorrectly implemented almost everywhere, including by Slack and other large companies we alerted i…
I do web app testing and report a similar issue as a risk rather often to my clients. You can replace Google below with many other identity providers. Imagine Bob works at Example Inc. and has email address bob@example.com Bob can get a Google account with primary email address bob@example.com. He can legitimately pass verification. Bob then gets fired for fraud or sexual harassment or something else gross misconduct…
I don't see this as a vulnerability: how is Google supposed to know that a person has left the company? You let them know by deleting the account.