Say you add a super_secret_internal_notes field. If you're writing a traditional backend, some human would need to explicitly add that to a list of publicly available fields somewhere (well, hopefully). For systems like Firebase, it's far too easy to have this field be created by frontend code that's just treating this as another piece of data in a nested part of a payload. But this can also happen on any system, if you have any JSON blob whose implicit schema can be added to by frontend development alone.

IMO implicit schema updates on any system should be consolidated and lifted to an easily emailed report - a security manager/CSO/CTO should be able to see all the super_secret_internal_notes as they're added across the org, and be able to immediately rectify security policies (perhaps even in a staging environment).

AFAIK Firebase doesn't do this - while there are pretty audit logs, there's not an automatic rollup of implicit schema changes: https://firebase.google.com/support/guides/cloud-audit-loggi...

(Also, while tongue in cheek, the way that the intro to a part of Firebase's training materials https://www.youtube.com/watch?v=eMa0hsHqfHU implicitly centers security as part of the launch process, not something ongoing, is indicative of how pervasive the issue is - and not at all something that's restricted to Firebase!)