v0 Apps Ship Fast.
Security Gaps Ship With Them.
v0 by Vercel generates production-ready Next.js apps in seconds - but the generated code consistently misses authentication on Server Actions, leaks env vars to the client, and creates open redirect vulnerabilities in middleware. We've found an average of 15 vulnerabilities per v0 app scanned.
Industry Data
Observed across scanned appsThe 6 Most Common v0 / Vercel Security Mistakes
v0-generated Next.js Server Actions are often created without auth guards. Any unauthenticated request can trigger privileged operations - data mutations, deletions, or admin workflows.
Vercel's Edge Config is sometimes used to store API keys and configuration. When fetched in client components or exposed via getServerSideProps without filtering, secrets become publicly accessible.
Accidentally prefixing secret env vars with NEXT_PUBLIC_ - or importing server-only modules in client components - exposes API keys, database connection strings, and auth secrets in browser JS.
v0-generated middleware often redirects based on user-controlled URL parameters without validation. Attackers craft URLs like /redirect?to=https://phishing.com to redirect your users to malicious sites.
Next.js API routes generated by v0 frequently lack CSRF token validation. State-changing endpoints (POST, PUT, DELETE) can be triggered by cross-origin requests from attacker-controlled pages.
Dynamic route handlers like /api/users/[id] generated by v0 often skip authorization checks - any authenticated user can read, modify, or delete any other user's data by changing the ID.
What PolyDefender Checks in v0 & Vercel Apps
v0 Generated Code vs. Production-Ready Security
| Pattern | v0 Default | Secure Version |
|---|---|---|
| Server Actions | No auth check | Session validation + role check |
| Environment vars | Mix of NEXT_PUBLIC_ and secret | Strict client/server separation |
| API route methods | Handles all HTTP methods | Explicit method allowlist |
| Dynamic route auth | Fetches by ID directly | ID ownership check per request |
| Middleware redirects | Redirect to req.nextUrl param | Only redirect to allow-listed paths |
| Error responses | Returns stack traces | Generic error messages only |
PolyDefender vs. Generic Scanners
Generic Scanner
- ✗Finds: OWASP basics only
- ✗Requires: code or repo access
- ✗Advice: generic remediation docs
- ✗Misses: Server Actions, Edge Config leaks
- ✗Context: none - same for every app
PolyDefender for v0
- ✓Finds: v0/Vercel-specific vulnerabilities
- ✓Requires: only your public app URL
- ✓Advice: Next.js-specific fix steps
- ✓Checks: Server Actions, CSRF, IDOR, open redirects
- ✓Context: built for how v0 generates Next.js code