v0 SECURITY CHECKLIST

v0 generates Next.js components and server actions in seconds. Two patterns make the output dangerous to ship as-is: it scaffolds with placeholder auth (mock users, hardcoded JWTs, “TODO: replace with real session”) that almost works in production, and it leans on NEXT_PUBLIC_ env vars to make examples self-contained — which inlines those values into the client bundle. The checklist below is what we look for first when we audit a v0-built Next.js app.

Treat Critical as launch-blocking. High is week-one. Medium is the cleanup once you have users.

How to use this checklist

Walk it once on a representative deploy preview, ticking items as you go. After each fix, ask v0 to “regenerate” something unrelated — v0 will sometimes silently revert a change when it touches an adjacent component. After the whole list passes, run a black-box scan against the deployed URL.

Critical (fix before launch)

1. Replace placeholder auth before connecting a real backend

Why it matters. v0 ships components with mock authentication: hardcoded users, fake JWTs, useUser() hooks that return { id: 'demo-user-1' }. Wire those components to a real database without replacing the auth layer and every request runs as demo-user-1. We have audited apps where the entire customer base shared one user record because nobody replaced the placeholder.

How to check. Search the codebase for demo-user, mock-user, 'TODO.*auth', getUserSession() returning a literal, and JWT strings that decode without a real iss/aud.

How to fix. Replace with a real auth provider (NextAuth, Clerk, Supabase Auth, Auth0). Confirm auth() returns the actual signed-in user before any database write.

2. Strip preview API keys before promoting to production

Why it matters. v0 wires components to the Vercel AI SDK or to third-party APIs using whatever key was set in the chat session — often a personal preview key. Promote the component to production and that personal key handles production traffic.

How to check. Open the deployed _next/static/ bundle in DevTools and search for sk_test, sk_live, re_, xoxb-, or any other recognizable key prefix. Then check Vercel project env for keys scoped to production that originated as preview.

How to fix. Move every API call to a server action or route handler so the key lives only in server env. Rotate any key that ever sat in a NEXT_PUBLIC_ var.

3. Add server-side validation behind every form

Why it matters. v0 forms validate with Zod or react-hook-form on the client and trust the body in the server action. The server action then writes to the database with whatever shape arrived. Drop the client validation in DevTools, submit garbage, and you can usually mass-assign fields the form never showed (isAdmin: true, creditBalance: 999999).

How to check. For every server action that takes form input, confirm the first line parses the input through a server-side schema (Zod, Valibot, manual). Confirm the schema explicitly lists allowed fields and rejects extras.

How to fix. Validate in the action; whitelist fields explicitly; never spread the input directly into a database call.

4. Enable RLS or row-scoping on the database

Why it matters. v0 components assume the database trusts the client. The first version of “fetch my todos” usually queries every todo and filters in the React component. Wire that to Supabase or Postgres without RLS and one user’s tab shows everyone’s data.

How to check. In Supabase: select tablename from pg_tables where schemaname = 'public' and rowsecurity = false. In raw Postgres: confirm every multi-tenant table has either an RLS policy or a server-side filter the client cannot bypass.

How to fix. Add per-table policies scoped by auth.uid() = user_id. In server actions, always filter by the authenticated user’s ID, never by an ID from the request body.

5. Audit server actions for SSRF and direct command injection

Why it matters. v0 will sometimes scaffold a server action that takes a URL from the form and fetch()es it (for previews, OG image generation, webhook tests). Without an outbound allowlist, that becomes SSRF — including against http://169.254.169.254/ and other internal metadata services.

How to check. Search server actions for fetch(formData.get('url')), fetch(input.url), and similar patterns. Test with http://localhost, http://169.254.169.254/, and file:///etc/passwd.

How to fix. Validate URLs against an allowlist (specific hosts) or reject private IP ranges explicitly. For OG-image fetches, use a hardened image proxy.

6. Remove debug toggles and admin shortcuts

Why it matters. v0 generates dashboards with helpful debug buttons: “Reset database”, “Seed test data”, “Login as admin”. They land in production because nobody removes the dev affordances when promoting the component.

How to check. Grep for process.env.NODE_ENV === 'development' and confirm every protected admin action is gated by a real authz check, not just an env flag. Check every /admin, /dev, /debug route.

How to fix. Delete debug routes from the production build, or gate them behind real role-based authz that fails closed when the role is missing.

High (fix in the first week)

7. Configure CSP headers on the host

v0 components don’t set CSP. Add a CSP via next.config.js headers that restricts script-src to 'self' and your domains, blocks inline scripts, and forbids unsafe-eval. CSP is your last line of defense against XSS that slips past validation.

8. Pin generated dependency versions

v0 installs whatever resolves at generation time. Pin every dependency in package.json and commit pnpm-lock.yaml / package-lock.json so production matches what you tested.

9. Verify webhook handlers check signatures

v0’s first-pass webhook handler usually skips signature verification. Stripe, Clerk, Resend, GitHub all sign their payloads — verify the signature before trusting the body.

10. Restrict who can publish v0 changes to production

v0 → Vercel deploys are seductively fast. Branch protection on main and required PR reviews catch the “I’ll just push this small fix” pattern that leads to incidents.

11. Audit ISR-cached pages for stale auth data

If v0 used revalidate with auth-dependent data, the cached page may include another user’s data. Either move auth-dependent rendering to dynamic, or scope the cache key to the user’s session.

12. Disable email enumeration in the auth provider

Whichever auth provider v0 wired up — Clerk, NextAuth, Supabase — confirm signup, password reset, and magic link return identical responses for “user exists” and “user does not exist.”

Medium (fix when you can)

13. Document which v0 versions are deployed where

Components evolve across regenerations. Tag releases with the v0 generation hash so you can correlate a regression to a specific generation.

14. Re-test security after every regeneration

v0 may rewrite security-critical code (auth checks, validation schemas) when you ask it to “improve the styling”. Re-run the smoke security tests after every regeneration that touches a server action.

15. Set up Vercel Analytics PII redaction

If you wired Vercel Analytics or Speed Insights into a v0 app, confirm the page URLs and titles you’re sending don’t include user IDs, emails, or session identifiers in the path.

16. Restrict team access by role on Vercel

Project-level roles control who can see env vars, deploy, and rollback. Audit who has Owner / Admin and downgrade where you can.

17. Audit any third-party iframes v0 added

Embed widgets (calendars, payments, video) often arrive as iframes. Add sandbox and a strict allow attribute so they can’t escape into your origin.

18. Set up audit logging on auth events

Whatever auth provider v0 wired up, ship its audit logs to where you can query them. You want a record of failed logins, password resets, and role changes long after default retention.

After every v0 regeneration

• Diff the entire component, including imports — v0 sometimes adds new packages.
• Re-check server actions for the placeholder-auth pattern.
• Search the diff for NEXT_PUBLIC_ additions and 'use server' deletions.
• Re-test auth-required server actions with the session cookie stripped.
• Confirm no new /admin, /dev, /debug route reappeared.

Common attack patterns we see in v0 apps

The shared demo user. v0 component shipped with getCurrentUser() => 'demo-user-1' because the chat used a placeholder. Production now has 5,000 users, all writing to the same row.

The NEXT_PUBLIC_ Stripe key. “Connect Stripe” prompt produces process.env.NEXT_PUBLIC_STRIPE_KEY for “convenience”. Live secret key is now in the client bundle, used by anyone who scrapes your JS.

The mass-assigned admin flag. Settings form doesn’t show an isAdmin field, but the server action does await db.users.update(formData). Attacker submits isAdmin=true and walks into the admin panel.

The OG-image SSRF. Server action fetches the URL from ?image= to generate a preview. Attacker passes http://169.254.169.254/latest/meta-data/iam/security-credentials/ and reads cloud credentials.

Related Resources

How to Secure v0

Step-by-step guide for hardening a v0-generated Next.js app — auth migration patterns, CSP setup, and the server-action audit checklist above in long form.

Is v0 Safe?

In-depth analysis of v0’s defaults — what it ships with, where the placeholders bite, and what we find on the day a typical v0 app launches.

Automate Your Checklist

A checklist tells you what to look for. A scanner tells you what’s actually broken in the deployed app right now. VibeEval drives a real browser through your v0 deployment, attempts the placeholder-auth and mass-assignment attacks above, and reports what got through — with file and line numbers to fix.