v0 Security Scanner
Is my v0 app secure?
v0 generates polished Next.js interfaces quickly, and a Next.js app has more ways to leak than a static site - serialized props travel to the browser, route handlers are public URLs, and a Server Action is an endpoint whether or not the code around it checks who called it. This scanner takes your deployed URL and inspects what that build actually serves and answers.
What we check on a v0 app
Sensitive data in serialized props
Reads the __NEXT_DATA__ payload your pages serialize into the HTML and flags secret-shaped values that were never meant to reach the browser.
Route handlers that answer anyone
Probes common API, debug, health, and admin-looking paths, and checks which HTTP methods a route unexpectedly accepts.
Read more →Keys in the client bundle
Matches your shipped JavaScript against key patterns for 30+ providers, catching a server secret that lost its server-only boundary.
Read more →Next.js dev surfaces in production
Requests build artifacts and dev-only routes such as published source maps and the webpack HMR endpoint, which should never answer on a production deployment.
Database reachable with a public key
If the app talks to Supabase or a Firebase Realtime Database, we test what those return using only the key present in your bundle.
Read more →Headers, cookies, and TLS
CSP, HSTS, frame and referrer protections, cookie HttpOnly, Secure and SameSite flags, cacheable auth pages, and certificate health.
Read more →How the v0 Security Scanner works
- Step 1
Paste your deployed v0 URL
The Vercel deployment or custom domain your app runs on. No v0 login, no GitHub connection, no environment variables, and no Ubserve account.
- Step 2
We inspect the deployment from the outside
We fetch the page and read its serialized props for secret-shaped values, download the JavaScript chunks it references and scan them for provider keys, then send unauthenticated requests to common route-handler paths, test which HTTP methods they accept, and check dev-only surfaces, headers, cookies, CORS, and TLS.
- Step 3
You get the report, partially unlocked
You see the issue count, a letter grade, and up to two findings in full, free. The rest - including the highest-severity findings and the copy-paste fix prompts - unlocks with a one-time report unlock or a plan.
Frequently asked questions
How do I know if my v0 app is exposing something?
Open the deployed page and view source. Everything a Server Component passed to a Client Component is serialized into the HTML and into the JavaScript payload, so search that output for a value you consider private - an internal ID, an email, a token. Then try a route handler in a private window: if GET /api/whatever returns data without a session, that route is public regardless of who links to it. This scanner performs both checks and reports what came back.
What is a Server Action, and why is it a security boundary?
A Server Action is a function marked with 'use server' that Next.js exposes as a callable endpoint so client code can invoke it directly. That convenience is the catch: the function is reachable over HTTP by anyone who can construct the request, not only by the button you wired it to. Whatever the surrounding page checked before rendering that button - that the user is signed in, that they own the record, that they are an admin - has to be checked again inside the action itself, because the action can be called without the page ever loading.
How does the scanner work?
It runs the standard Ubserve public scan against your deployed URL. We fetch the page, parse its serialized props for secret-shaped values, follow its script chunks and scan them against provider key patterns, and probe common route-handler, debug, and build-artifact paths with unauthenticated requests. We also vary the Origin header to test CORS, check which HTTP methods routes accept, and read cookies, security headers, and the TLS certificate.
Is it free? Do I need to sign in?
The scan is free and you do not need an account to run it. You get the issue count, a letter grade, and up to two findings shown in full - location, evidence, and severity - at no cost. The rest of the report stays locked, including the highest-severity findings and the copy-paste fix prompts you can hand to your AI coding tool. Unlocking everything is a one-time payment for that report, or a plan if you want repeat scans and monitoring.
Does Ubserve see my v0 project or source code?
No. This scan only reads what your app already serves to the public: the HTML at your URL, the JavaScript bundles that page links to, HTTP response headers, TLS certificate details, and public DNS records. We never ask for a repository, a database password, a service-role key, or an app login, and we cannot see private source code or authenticated pages. When we find a secret in your bundle, we found it because your browser downloads it too - anyone viewing your site can read the same bytes.
Will scanning break my deployment?
No. Every request is a read against your public URLs - no writes, no account creation, and no Server Action invoked with a mutating payload. Probes are paced a couple at a time with pauses between them, so the traffic reads as ordinary rather than as a burst your host should rate-limit.
What founders say
5.0 out of 5 - Ubserve, from 3 reviews
“Helped me find a critical database issue that would've done real damage. I recommend it for every founder.”
“Caught a critical CSP issue on my frontend within minutes. Don't ship without a scan.”
“The free scan took under 60 seconds to find real issues in my project.”
Other free tools
See all tools →
AI BuildersBolt.new Security Scanner
Checks a deployed Bolt.new app for env values that reached the client bundle and endpoints that trust the browser.
Open tool →
AI BuildersCursor Security Scanner
Checks a Cursor-built app for the protections the model never mentioned: throttling, CSRF tokens, and access control.
Open tool →Exposed API Key Scanner
Downloads your deployed JavaScript and matches it against key patterns for 30+ providers, from Stripe to OpenAI to AWS.
Open tool →Keep reading
- v0 security checklistSecuring apps built with v0 and Next.js.
- Next.js Server Action securityWhy the action, not the page, is the boundary.
- Broken access control in AI-built appsThe most common failure in generated route handlers.
- How to remove exposed API keys from your frontendRestoring the server-only boundary around a secret.
- Pre-deploy security checklist for vibe-coded appsThe last pass before you ship.
Run the v0 Security Scanner
Paste your URL and see what your app is handing to the public. Free, no account, no repo access.