something worth knowing if you run a SaaS, especially one built fast or with AI tools. The single most common API vulnerability is embarrassingly simple your app checks that a user is logged in, but never checks that the specific record they're asking for actually belongs to them. So a logged-in user changes an ID in a request (say /invoice/123 to /invoice/124) and the app hands back a stranger's data. No error, no log. It looks perfect in every demo because you only ever open your own data. It ...