IS A0.DEV SAFE? SECURITY ANALYSIS | VIBEEVAL

Is a0.dev safe? The short answer

a0.dev the platform is safe. Apps built with a0.dev are safe when the developer treats the mobile client as untrusted and hardens the backend. The platform generates modern React Native / Expo code and wires it to capable backends (typically Supabase or Firebase). But the generated apps consistently enforce security in the one place it cannot be enforced — the client — while the backend rules, secret handling, and token storage that actually matter ship permissive or default. Each gap is a known fix; collectively they are the difference between a demo and a store-ready app.

Why mobile changes the security model

An a0.dev app is not a website. Three properties of shipped mobile binaries drive every item below:

• The whole client ships to the attacker. Anyone can download your app, unzip the bundle, and read every string in it — API keys, endpoint URLs, feature flags, gating logic. Nothing in the binary is secret.
• Releases cannot be recalled. A leaked secret in a web deploy is rotated in minutes. A leaked secret in a released binary lives on users’ phones; rotating it breaks old installs, and archived copies keep the old value forever. Secrets must be server-side from day one.
• Client checks are suggestions. Auth screens, premium gates, and role checks in React Native code do not bind an attacker who calls the backend directly with the extracted config.

The consequence: the backend rules — Supabase RLS or Firestore security rules or endpoint auth — are the actual security boundary. Everything else is UX.

The a0.dev generation pattern

a0.dev generates working apps fast — prompt, preview on your phone, iterate in chat. The AI prioritizes “this works in the preview” over “this survives an attacker.” That has a predictable cost:

• Backend rules lag the schema. New tables and collections appear as you prompt; policies and rules for them often don’t.
• Keys land where the code is. When a feature needs OpenAI or Stripe, the generated call is made from the client, key included.
• Tokens go to AsyncStorage. The default, unencrypted storage — not Keychain/Keystore.
• Gates live in the UI. Premium and admin checks are React conditionals, not server checks.
• Endpoints trust the caller. Generated CRUD endpoints skip auth or skip ownership.

These are not bugs in a0.dev; they are characteristics of AI generation under “make it work” pressure. Knowing the pattern is most of the fix.

The 6 areas to harden in every a0.dev app

1. Backend authorization (RLS / Firestore rules)

The client config in your bundle lets anyone query the backend directly. If the backend allows it, the data is public — regardless of what the app’s UI shows.

Fix. Deny by default, then write explicit per-table policies:

-- Supabase: user-scoped table
alter table projects enable row level security;

create policy "owners read their projects"
  on projects for select
  using (auth.uid() = owner_id);

create policy "owners write their projects"
  on projects for all
  using (auth.uid() = owner_id)
  with check (auth.uid() = owner_id);

For Firebase, the equivalent Firestore rules scope reads and writes to request.auth.uid. Test by querying with the extracted client config and no session, then with a second account. See the Supabase RLS checker and Firebase scanner.

2. Secrets out of the bundle

The anon key and Firebase config are fine in the client. Everything else is not.

Fix. Audit source, app.json extra fields, and the exported bundle:

grep -rE 'sk_(live|test)_|sk-[A-Za-z0-9]{20,}|service_role' \
  . --exclude-dir=node_modules

Move every secret-requiring call behind an edge function or server endpoint that holds the key. Rotate anything that ever appeared in a build — and remember rotation does not fix installed copies, which is why the server-side pattern must be in place before first release, not after the leak.

3. Token storage (SecureStore, not AsyncStorage)

AsyncStorage is plaintext on disk. Session and refresh tokens there are one backup-extraction away from account takeover.

Fix. Use hardware-backed storage:

import * as SecureStore from "expo-secure-store";
import { createClient } from "@supabase/supabase-js";

const supabase = createClient(url, anonKey, {
  auth: {
    storage: {
      getItem: (k) => SecureStore.getItemAsync(k),
      setItem: (k, v) => SecureStore.setItemAsync(k, v),
      removeItem: (k) => SecureStore.deleteItemAsync(k),
    },
  },
});

4. Endpoint auth and ownership (BOLA)

Generated endpoints frequently check nothing, or check the session but not ownership. Any signed-in user fetching any record by ID is the most common finding in AI-generated CRUD — see BOLA in AI-generated CRUD.

Fix. Every endpoint validates the session, then confirms the resource belongs to the caller:

// Supabase edge function shape
const { data: { user } } = await supabase.auth.getUser(jwt);
if (!user) return new Response("Unauthorized", { status: 401 });

const { data: row } = await admin.from("projects")
  .select().eq("id", id).single();
if (!row || row.owner_id !== user.id)
  return new Response("Not found", { status: 404 });

Manual test: user B requests user A’s resource ID directly against the backend. Expect 403/404.

5. Server-side entitlements

Premium flags in app state are patchable; premium endpoints without server checks are free.

Fix. The backend verifies the entitlement — a server-stored subscription flag, a validated App Store / Play receipt, or a RevenueCat entitlement check — before serving premium content or accepting privileged writes. Strip fields like role, is_premium, and credits from any user-writable path.

6. Transport and logging hygiene

Generated Expo apps have no certificate pinning (any device-trusted CA can intercept) and log request/response bodies to the console.

Fix. Never ship with TLS verification disabled; consider pinning via a config plugin for sensitive apps. Strip console.log from release builds with babel-plugin-transform-remove-console. Validate OAuth deep links: prefer universal links / app links over custom schemes, and check state on callbacks.

Pre-launch a0.dev checklist

A practical sequence before submitting to the stores:

1. RLS enabled with explicit policies on every Supabase table (or equivalent Firestore rules on every collection).
2. No secret keys in source, app.json, or the exported bundle; all secret-requiring calls server-side.
3. Tokens in SecureStore, including the Supabase client storage adapter.
4. Every generated endpoint checks auth and ownership.
5. Premium and role gating enforced server-side; privileged fields stripped from user writes.
6. Input re-validated at the server boundary on every endpoint.
7. OAuth redirects restricted; state validated; universal links for production callbacks.
8. Console logging stripped from release builds; no TLS-verification bypasses.
9. Dependencies verified against package hallucination.
10. Run VibeEval against the backend for the dynamic pass.

a0.dev vs web app builders — security positioning

• a0.dev. Mobile-first React Native / Expo generator. Failure modes concentrate in backend rules, bundle-embedded secrets, token storage, and client-only gating — amplified by the fact that mobile releases can’t be recalled.
• Lovable / Bolt. Web generators on Supabase-style backends. Same RLS and BOLA failure modes, but a leaked web secret is rotatable in minutes.
• Base44. Full-stack web with built-in entities; failure modes are entity permissions and function auth.

Pick the tool whose failure modes you can audit. For a0.dev, that means someone willing to write backend rules and keep every secret server-side — the generator will not do it for you.

The verdict

a0.dev produces working mobile apps remarkably fast. Security is not what it optimizes for. Treat every a0.dev-generated app as needing a review before store submission — backend rules as the real auth boundary, zero secrets in the bundle, SecureStore for tokens, server-side entitlements, and auth plus ownership on every endpoint. The list is mechanical and scannable. Run it before launch, every launch — because on mobile, you don’t get to quietly fix it after.

Related resources

• How to Secure a0.dev — step-by-step hardening guide
• a0.dev Security Checklist — pre-launch checklist
• Vibe Code Scanner — automated scan for AI-generated apps
• Token Leak Checker — find exposed keys in your app
• Vibe Coding Vulnerabilities — full vulnerability taxonomy across AI tools
• OWASP Top 10 for AI Code

Scan your a0.dev app

Let VibeEval scan the backend your a0.dev application talks to for the missing-rules, BOLA, entitlement-bypass, and credential-leakage patterns that AI generators most often leave in.