My Android app uses to sign in to access the data in Real-time database. I don't want anyone to make any changes in the database outside of my app. If someone got the Firebase JSON file by extracting it from the Android APK file and if they have an account in my app, can they create a web app (or a mobileapp) to login with the credential and access my app database?
I have set the security rules such that user can access only what they are suppose to access and I have done validations (like isNumber) but only basic validations can be done in the server side.
So if he can login outside of my app, he will be able to bypass the validations I do in the app.
Also additionally, I want to know if someone got access to that JSON file, can he also create new users?