Supabase, Firebase, Auth0, and AI-generated apps: common configuration errors

Supabase, Firebase, and Auth0 allow you to quickly build what an MVP almost always requires: databases, login, roles, storage, APIs, callbacks, email, and integrations. By connecting these to an AI app builder or a coding agent, a prototype can become credible in just a few days. The fragile part is not the provider itself, but the configuration that holds together the generated frontend, the managed backend, and the actual data.

The typical risk is an app that works in a demo but fails to correctly separate users, tenants, roles, buckets, keys, and environments. AI tools tend to solve the immediate problem — reading a table, passing a login, uploading a file, closing a CORS error, completing a redirect — without necessarily considering the big picture. Before going live, it is therefore necessary to verify whether those choices respect the principle of least privilege, data isolation, and server-side controls.

This article is aimed at technical founders, developers, and PMs who have used Lovable, Bolt.new, v0, Replit Agent, Cursor, Copilot, Codex, Claude Code, or other AI tools to connect a web app to Supabase, Firebase, or Auth0. The practical question is: is the managed backend configured to handle real users, real data, and direct API requests?

The problem isn’t using a BaaS: it’s using it without clear boundaries

Backend-as-a-service and identity providers are useful, mature tools. Supabase offers Postgres databases, Auth, Storage, Edge Functions, and controls like Row Level Security. Firebase offers Firestore, Authentication, Cloud Storage, Functions, and Security Rules. Auth0 manages identities, logins, tokens, callbacks, and integrations with applications and APIs.

The critical point is shared responsibility: the provider protects the platform and offers robust functions, but it cannot know if the orders table should only be readable by the owner, if one tenant should not see another’s files, if a staging callback needs to be removed, if a service role key has ended up in the frontend, or if an admin role created for the demo is still too powerful. When the app is generated with AI, this distinction becomes even more important, because the code may look coherent, the UI may hide unauthorized actions, and tests may pass, but real security depends on rules, policies, tokens, and direct API calls, not just the path visible in the interface.

Supabase: RLS is not an optional detail

In Supabase, Row Level Security (RLS) is the central control to prevent different users from reading or modifying unauthorized rows. If an AI-generated app creates tables, queries, and client SDKs without coherent policies, the risk is that an authenticated user could access data that does not belong to them.

The most dangerous case is a table exposed with no RLS or overly permissive policies. A using (true) policy might be acceptable only for public data intended to be read by everyone, but it becomes critical for profiles, orders, documents, workspaces, messages, tickets, invoices, or multi-tenant records. Even insert, update, and delete operations must have coherent conditions, not just select.

To verify Supabase, it is not enough to open the dashboard and see that the app works. You need to create two users, two organizations, and similar data, then try cross-account reading, modification, deletion, and export. It is important to check auth.uid(), tenant_id, membership, roles, and ownership in every policy, while also verifying RPC functions and views, which can become shortcuts capable of bypassing the expected authorization model.

Supabase: anon key, service role key, and the frontend

The anon key is designed to be used by the client, but its security depends entirely on policies: if RLS and storage policies are correct, the anon key only allows what the policies permit. The service role key is a different matter — it has elevated privileges and must never end up in the frontend, the bundle, source maps, logs, or the repository.

AI tools can blur this boundary. If a query fails due to insufficient permissions, the assistant might suggest a solution that uses a more powerful key or moves a call to the wrong place: the result works, but it bypasses the security model. This often happens when the team wants to quickly connect a React or Next.js frontend to Supabase. Before deploying, it is therefore necessary to inspect frontend bundles, public variables, .env files, build logs, serverless functions, and platform settings. Variables with client-side prefixes like NEXT_PUBLIC_ should only contain values intended for the browser, and any exposed service key must be rotated.

Supabase Storage: buckets, policies, and private files

Many AI-generated apps add file uploads to complete a demo — avatars, documents, attachments, images, PDFs, exports, screenshots, or datasets. If Supabase Storage is configured with public buckets or open policies, the app’s login does not truly protect the files.

Verification must include who can upload, read, download, delete, and overwrite files. A user must not be able to modify the path or ID to download another user’s documents, and in a multi-tenant app, every path or metadata must be linked to a tenant and membership, not just a filename generated by the client. Attention must also be paid to previews and signed URLs: a file might be private but have an accessible preview, a link with an excessive duration, or metadata that reveals sensitive information. For non-public files, use private buckets, policies per user or tenant, signed URLs with limited duration, and test downloads with different accounts.

Firebase: open Security Rules are the weakest point

Firebase makes it fast to create apps with realtime data, authentication, and storage, but that speed depends on Security Rules. Firestore and Cloud Storage must know who can read, write, update, and delete every document or file: if rules are left open for development, a working app can expose everything.

Temporary rules are frequent in accelerated projects: allow read, write: if true, overly generic checks on request.auth != null, conditions that only verify if the user is logged in, overly broad path wildcards, or the absence of checks on owners, roles, or tenants. A generated UI might show only correct data, but the Rules decide what happens when someone calls Firestore or Storage directly. Before going live, review Firestore Rules and Cloud Storage Rules separately, adopt a default-deny approach, and open only the necessary paths. Test operations with different users, different roles, other users’ documents, missing tokens, expired tokens, and malformed data. If the app uses Cloud Functions as a server-side layer, verify that the functions do not reintroduce broader access.

Firebase App Check: useful, but no substitute for auth and authorization

Firebase App Check helps reduce traffic from unauthorized or counterfeit clients to Firebase services and compatible backends, and it is useful when the app is exposed and you want to reduce API, storage, or function abuse. However, it does not decide whether a user can read another user’s document.

App Check should be treated as an additional control: authentication, Security Rules, and application-level authorizations remain necessary. If a rule allows any logged-in user to read a collection, App Check does not correct the access logic but only limits part of the abuse from unexpected clients. For AI-generated apps, evaluate App Check when you have a public frontend, uploads, frequent calls to Firebase services, serverless functions, or sensitive APIs. Enable enforcement where appropriate, monitor unverified requests, and verify that the app does not depend on App Check to protect data that should be protected by Rules.

Auth0: a successful login does not mean correct authorization

Auth0 solves an important piece: authenticating users, managing sessions, issuing tokens, and integrating identity providers. However, login does not prove that the user can perform a specific action in the app. After authentication, the backend must verify the audience, issuer, signature, expiration, scope, roles, permissions, ownership, and tenant.

A common error in AI-generated apps is using Auth0 as if the token were enough to authorize everything. If the code only checks that a logged-in user exists, APIs and data remain vulnerable to broken access control. If roles or claims are interpreted on the frontend without server-side verification, a user can bypass controls by calling APIs directly. Before deploying, it is therefore necessary to verify which APIs accept access tokens, which audience is expected, which scopes are requested, how roles and permissions are mapped, and where the token is verified. Every sensitive route must apply server-side controls, not just conditional rendering in the interface.

Auth0: callbacks, redirects, and preview domains

During AI-assisted development, the team often adds local domains, preview URLs, Vercel environments, temporary redirects, and staging callbacks. Auth0 requires Allowed Callback URLs to be configured, but if the list grows without cleanup, it can become too permissive.

The risk is accepting redirects or callbacks that are no longer needed, old preview domains, broad wildcards, inconsistent logout URLs, or web origins not aligned with real environments. In OAuth/OIDC flows, redirects and session state are part of security, not just user experience. Before going live, review Allowed Callback URLs, Allowed Logout URLs, and Allowed Web Origins: leave only real domains, controlled staging, and necessary URLs; remove temporary previews and avoid broad wildcards.

Dev, staging, and production: three environments, three perimeters

MVPs created with AI often share projects, databases, or keys between development and production. This simplifies the demo, but makes the transition to real data dangerous: a preview deploy can write to the production database, a test can delete real data, a staging key can read client files, or a local callback can remain active in production.

For Supabase, Firebase, and Auth0, separate environments decisively: different projects, different databases, different storage, different keys, different callbacks, separate test users, and synthetic data outside of production. Policies must be versioned and controlled per environment. This separation is also a control against AI agents: if the agent works on a development environment with limited keys, a configuration error has a minor impact; if it works with production credentials, every command or generated file can become an incident.

Testing policies: UI, API, and SDK

A BaaS or Auth configuration cannot be validated by looking only at the interface. You need to test APIs, SDKs, and rules directly, because the UI might prevent an action while Firestore, Supabase, or a server-side API might still accept it.

Prepare negative cases: non-logged-in user, user with a low role, user from another tenant, expired token, manipulated ID, another user’s file, invalid callback, missing scope, wrong audience, upload outside of path, unauthorized field update. Each test must demonstrate that the data is denied at the right point. For Supabase, test client-side queries, RPC, Storage, and exposed APIs; for Firebase, test Firestore, Storage, and Functions; for Auth0, test server-side routes, protected APIs, tokens with insufficient scope, and redirects. Automated tests are useful, but go-live also requires manual, abuse-oriented verification.

Common errors in Lovable + Supabase apps

Lovable is a recurring case because it allows for the rapid construction of full-stack apps and is often connected to Supabase. When a quickly generated MVP uses Supabase as a real database without a policy review, the risk is concentrated on RLS, buckets, keys, and queries generated to make the demo work immediately.

Typical errors include tables created to make a feature work without correct RLS, buckets used for uploads with broad policies, service role keys confused with anon keys, Edge functions or APIs that do not verify the tenant, and queries that filter on the frontend instead of in the database or backend. Before connecting real data, check the generated schema, migrations, policies, buckets, environment variables, and server-side functions. Then test two users and two workspaces: if the app is multi-tenant, do not publish until a user from one tenant has been blocked from attempting to read another’s data.

When AI corrects an error by making the configuration more permissive

Many misconfigurations stem from an apparently reasonable correction. The query returns no data, the upload fails, the login returns to the wrong page, an API call receives a 403, a serverless function fails to read a table. The assistant proposes a change that unlocks the flow — widening a policy, adding a domain, making a bucket public, using a more powerful key, moving a call to the client, or simplifying a Firebase rule — and the fix resolves the symptom, but not necessarily the security model.

If a Supabase policy is widened to let a screen pass, you need to verify which other users can read that table. If a Firebase Rule changes from an owner check to a logged-in user check, you need to test cross-access. If an Auth0 callback is added for a preview, it must be removed when no longer needed. If a service role key resolves an error, the right question is why the policy did not allow the correct action. Every change suggested by AI regarding policies, rules, callbacks, scopes, buckets, CORS, service keys, and public variables should be treated as a sensitive change: the diff might be small, but changing an allow read or a callback can expose more data than an extensive refactoring.

What to fix before going live

Some findings on Supabase, Firebase, and Auth0 must block the release. Missing RLS on tables with private data, open Security Rules, service role keys in the frontend, unexpected public buckets, overly permissive callbacks, unverified server-side tokens, and staging environments connected to production data are not ordinary technical debt: they are conditions that can expose data as soon as the app receives real traffic.

Remediation must be verifiable. Enable or rewrite RLS and then test different users and tenants. Fix Firebase Rules and then test direct reading and writing. Restrict Auth0 callbacks and then verify login, logout, and redirects only in the intended environments. Move private keys out of the frontend and then check bundles and logs. If a bucket changes from public to private, also verify previews, signed URLs, and old shared links.

Other improvements can be planned after go-live only with a clear residual risk: better documenting policies, adding automated tests for Rules, strengthening alerts, further separating internal roles, or improving variable naming. However, the minimum control over real data must be closed before users and customers enter the system.

When an independent verification is needed

An internal review might suffice if the app uses synthetic data, has no external users, does not expose uploads, has no complex roles, and the team knows Supabase, Firebase, or Auth0 well. In that case, the work is to verify RLS, Rules, callbacks, and keys before they become production.

Instead, an independent verification is needed when the app handles real data, uses multi-tenancy, exposes APIs, manages files, connects payments or CRMs, uses administrative roles, or when the configuration has been partially generated by AI and no one has tested the policies against abuse. The same applies if the team cannot clearly distinguish what is controlled by the provider and what remains the app’s responsibility.

How ISGroup can verify AI apps with Supabase, Firebase, and Auth0

ISGroup can verify the app’s real-world behavior and the configurations that connect the frontend, BaaS, identity provider, APIs, and cloud. The goal is to understand if the rules truly protect data when the user does not follow the flow intended by the UI.

If the AI app uses…	Main risk	Recommended control
Web app, API, auth flow, upload, or public routes	External abuse, BOLA, IDOR, auth bypass	Web Application Penetration Testing
Supabase policies, Firebase Rules, middleware, queries, or token management in code	Weak authorization logic or regressions	Code Review
BaaS/cloud projects, buckets, storage, IAM, keys, environments, and service accounts	Misconfiguration or excessive privileges	Cloud Security Assessment
Services, endpoints, and components exposed with known versions or configurations	Known vulnerabilities and exposed technical surfaces	Vulnerability Assessment
Continuous use of AI builders and coding agents on successive releases	Non-repeatable controls on policies, auth, and deploys	Software Assurance Lifecycle

The choice of control depends on where the risk lives: exposed behavior, code, policies, cloud, storage, or the release process. For apps already online, it is advisable to test real behavior, not just read the configurations.

Have you connected an AI-generated app to Supabase, Firebase, or Auth0 and need to take it online? ISGroup can verify RLS, Security Rules, callbacks, tokens, storage, APIs, roles, and configurations before go-live.

Evidence to prepare

Prepare environment URLs, repositories, Supabase/Firebase/Auth0 projects, database schemas, RLS policies, Firebase Rules, buckets, configured callbacks, preview domains, environment variables, server-side functions, user roles, tenants, APIs, and parts generated by AI.

Test accounts are also needed: anonymous user, standard user, admin user, and, if applicable, two tenants or two workspaces. Without realistic test accounts and data, it becomes difficult to verify BOLA, storage policies, and callbacks. If you have already received alerts about exposed keys, permissive rules, public buckets, or unexpected callbacks, include them in the review: often the visible finding is only the symptom of an authorization model that needs to be corrected.

Checklist before go-live

• RLS active on every Supabase table with non-public data.
• Specific Supabase policies for select, insert, update, and delete.
• No service role keys in the frontend, logs, or repository.
• Supabase Storage with private buckets and policies per user or tenant.
• Firestore Security Rules and Cloud Storage Rules without temporary openings.
• Firebase App Check evaluated or enabled where it reduces abuse.
• Auth0 callbacks, logout URLs, and web origins allowlisted without broad wildcards.
• Audience, scopes, roles, and permissions verified server-side.
• Dev, staging, and production separated for projects, keys, data, and callbacks.
• Manual tests with different users, roles, and tenants on APIs, SDKs, uploads, and exports.

Frequently Asked Questions

• Are Supabase and Firebase secure by default?
• They are robust platforms, but your app’s security depends on the RLS, Security Rules, storage policies, roles, queries, keys, and callbacks configured in the project.
• Can the Supabase anon key be in the frontend?
• Yes, if it is used as intended and if RLS and policies correctly limit access. The service role key, however, must never be in the frontend.
• Does Firebase App Check replace authentication and authorization?
• No. App Check helps verify that requests come from expected clients, but it does not decide what data a user can read or modify.
• Is Auth0 enough to protect APIs?
• No. Auth0 authenticates and issues tokens, but APIs must verify tokens, audience, scopes, roles, ownership, and tenants server-side.
• When is a Web Application Penetration Testing needed?
• When web apps, APIs, logins, uploads, callbacks, or routes are exposed online. WAPT verifies real behavior from the outside, including role abuse and direct access to endpoints.
• Which errors block go-live?
• Missing RLS on private data, open Security Rules, service role keys in the frontend, unexpected public buckets, overly permissive callbacks, untested tenant isolation, APIs that only check login, and production environments shared with staging.

Useful sources and references

• Supabase Row Level Security: https://supabase.com/docs/guides/database/postgres/row-level-security
• Supabase Security: https://supabase.com/docs/guides/security
• Supabase API security: https://supabase.com/docs/guides/api/securing-your-api
• Firebase Security Rules for Cloud Storage: https://firebase.google.com/docs/reference/security/storage
• Firebase Firestore Security Rules: https://firebase.google.com/docs/firestore/security/rules-structure
• Firebase App Check: https://firebase.google.com/docs/app-check
• Auth0 redirect after login: https://auth0.com/docs/login/redirect-users-after-login
• Auth0 scopes: https://auth0.com/docs/scopes
• Auth0 access tokens: https://auth0.com/docs/security/tokens/access-tokens/get-access-tokens
• Auth0 refresh token rotation: https://auth0.com/docs/secure/tokens/refresh-tokens/refresh-token-rotation
• OWASP API Security: https://owasp.org/www-project-api-security/