By v0 apps usually break behind the interface: server actions and API routes that never check who the user is, and secrets exposed through NEXT_PUBLIC_ variables. The generated UI code is often a good starting point.
What v0 builds
v0, from Vercel, generates React and Next.js code with Tailwind CSS and shadcn/ui and deploys to Vercel. Databases and sign-in come from integrations such as Supabase or Neon.
Where v0 apps usually break
No secret keys reach the browser
Open your live app, then DevTools, Sources, and search the loaded JavaScript for sb_secret_, sk_live_, sk-proj- and sk-ant-. Older Supabase keys are long tokens starting with eyJ: decode the middle part of each on your own machine, and if it contains "role":"service_role", your secret key is public. A publishable or anon key in the browser is expected.
Admin actions are checked on the server
Hiding an admin button is not protection. Call the admin endpoint as a normal user and confirm it is refused.
Prices and plans come from the server
If the price or plan ID is sent from the browser, someone can edit it. The server should look it up.
Input is validated on the server
Forms that only check input in the browser accept anything sent directly to the API.
The flows that make money have tests
Sign-up, checkout and the core action. A few end-to-end tests catch most regressions from new prompts.
AI and paid API calls have per-user limits
Without a cap, one user or one bot loop can spend your monthly budget in an hour.
Check it yourself
- List every environment variable starting with
NEXT_PUBLIC_. Those are sent to the browser, so none of them can be a secret. - Open each server action and API route and confirm it checks who the user is before reading or changing data.
- Confirm prices, plans and roles are read on the server, not taken from the request.
- Add limits to any route that calls an AI model.
When to call an engineer
Call an engineer when server actions change data without checking the user, or when the app needs a real back end beyond what the integrations cover.
A one-off check costs $49 to $800. Fixing and hardening an app costs $1,500 to $15,000 and takes 1 to 8 weeks, based on the prices companies publish.
Top-rated companies for v0 apps
Ranked by our score: published prices, scope of work, AI tools named, timing and a low-risk first step. How we score.
- 1Afterbuild Labs10.0/10Best for: A check before launchFree first step · from $49
- 2Redlab10.0/10Best for: A full rescue by one team that keeps buildingFree first step · from $490
- 3Vibe Code Rescue (Lev Arakelyan)9.0/10Best for: A one-off check and a cleanupFrom $299
Questions
Is v0 code production-ready?
The UI code is often a good starting point. Access checks, validation, tests and error handling usually need to be added before launch.