Firebase is a shitshow. I say this as someone who really tried to like it and sadly built a project for a client using it. Other than this security vuln, the issues vs. just using postgres are: * It is more work! Despite being a backend as a service it is much less code to just write a simple API backend for your thing both in time to do it and time to learn how to do it. Think of Firebase as being on the abstraction…
I remember having some issue, and thought: well, it's JS, let me just check the source like I normally would! Only to find out that you couldn't browse the full client source code anywhere. At that point my only option was to reverse engineer the minified source which just seemed silly and like a waste of time.
Firebase moat has nothing to do with their frontend library, which anyone could reverse engineer with a little bit of time. And yet they still kept it closed source. I don't know if anything has changed since then, but that was the primary reason why I lost interest in the service.