How to secure an application with a backend on Firebase?

Question

firebase

In my web app, users will have a balance. How can I add it to the database so that an attacker cannot install it arbitrarily? I set the security rules settings in such a way that an authorized person can only create, but not update in the database. But it still turns out that when registering, I create an entry in the database through the frontend, and so it will be possible to make an entry in the "balance" field.

Answer 1

It seems to me, only having removed creation of the user to other place. So that the resulting record object is not created in the application.
I looked briefly, there is Cloud functions, maybe it will be possible to make such a request there?