I'm starting work with Web Applications and I build a VueJS app. So far I'm using the Firebase Authentication to auth the users and access the Firestore. Here I've a big problem: the Firebase config data are exposed on the browser tools, so anyone can see the sensitive information and I suppose that can do operations on database: CRUD.

Exposed data:

var firebaseConfig = {
    apiKey: "",
    authDomain: "",
    databaseURL: "",
    projectId: "",
    storageBucket: "",
    messagingSenderId: "",
    appID: "",
};

As my application has only Client-Side I have no idea how solve it. Besides that I going to use Google Cloud SQL and I got the same problem: authentication. There are some securely way to use only Client-Side application and iterate with Cloud SQL, Firestore and so on? I'm seeking for a cheap way to make my application, and to use a Backend I'll need spend a lot of money with VMs: EC2 (AWS) or App Engine (Google).

Please, someone can guide me on this scenario?