What is the most common security mistake in v0 apps?

Unprotected server actions and API routes. v0 generates Next.js server actions that are callable by anyone on the internet, and the generated code frequently omits the session check - so any visitor can invoke them directly. Every server action and route handler that touches data must verify who is calling.

Is middleware enough to protect my Next.js app?

No - middleware is a convenience gate, not a security boundary. CVE-2025-29927 demonstrated middleware-based auth being bypassed entirely with a crafted header. Each server action, route handler and database query should re-check the session itself.

Can I run my commercial v0 app on Vercel's free plan?

No - Vercel's Hobby tier prohibits commercial use. Commercial apps need Vercel Pro (from $20/user/month) or another host whose free tier allows commercial projects. Also turn on Vercel Spend Management: usage pricing means one viral day can produce a $500+ surprise bill.

v0 App Security Checklist

Your v0 app deploys - this checks whether it defends. 19 Next.js/Vercel-specific checks covering server actions without auth, NEXT_PUBLIC_ secret leaks, middleware-only protection, and the Vercel plan and spend traps that catch v0 builders. Independent tests find 40-62% of AI-generated code contains vulnerabilities.

By Carl Mills - cloud & security engineer • Last updated 9 July 2026 • Progress saves in your browser • free personalized PDF print-out.

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v0 security FAQ

Is middleware enough for auth?

No - it's a gate, not a boundary (CVE-2025-29927 made that famous). Every server action and route handler should re-check the session before touching data.

What does NEXT_PUBLIC_ actually do?

It deliberately exposes the variable to the browser. Fine for a public analytics id; never for an API secret. Everything without the prefix stays server-side.

What next once everything's ticked?

Run the general 12-point AI-app launch checklist, sanity-check your Vercel costs, and push the code to your own GitHub.

Want a professional pass?

A fixed-scope security review covers every item here plus the ones only an engineer would find - with a prioritised fix list.

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