TL;DR
v0 by Vercel generates React and Next.js UI components from text descriptions. It's great for building interfaces quickly, but the components are frontend-only. Security issues to watch for include XSS vulnerabilities, improper data handling, and missing input validation. Always add proper backend validation when connecting v0 components to real data.
What is v0?
v0 is Vercel's AI-powered tool that generates React components from natural language descriptions. You describe what you want ("a pricing table with three tiers") and v0 creates the code. It's focused on UI components, not full applications.
Key things to understand about v0:
- Frontend only: v0 generates UI components, not backend logic
- React/Next.js based: Components use React with Tailwind CSS
- No database integration: You add data connections yourself
- Vercel deployment ready: Components work well with Vercel hosting
Security Model of v0
v0's security is different from full-stack tools like Bolt or Lovable because it only generates frontend components. The security of your final app depends heavily on how you connect these components to your backend.
Key point: v0 components are building blocks. They don't have inherent security because they're just UI. Your security comes from how you use them.
Common Security Issues in v0 Components
1. Unescaped User Data (XSS Risk)
When v0 generates components that display data, it usually uses React's built-in escaping. But watch for dangerouslySetInnerHTML:
// If v0 generates this, be careful
<div dangerouslySetInnerHTML={{ __html: userContent }} />
// This bypasses React's XSS protection
// Only use if you've sanitized the HTML yourself
Solution: If you need to render HTML, sanitize it first:
import DOMPurify from 'dompurify';
// Sanitize before rendering
const cleanHTML = DOMPurify.sanitize(userContent);
<div dangerouslySetInnerHTML={{ __html: cleanHTML }} />
2. Client-Side Only Validation
v0 might generate forms with validation, but it's all client-side. Users can bypass this:
// This validation runs in the browser
// Users can disable JavaScript and skip it
const handleSubmit = (data) => {
if (data.email.includes('@')) {
submitToAPI(data);
}
};
Rule: Never trust client-side validation alone. Always validate on the server too.
3. Exposed API Keys in Client Code
If you add API integrations to v0 components, don't put secrets in the frontend:
// BAD: API key visible in browser
const response = await fetch('https://api.service.com/data', {
headers: {
'Authorization': 'Bearer sk_live_abc123...'
}
});
// GOOD: Call your own API route
const response = await fetch('/api/get-data');
// Then in your Next.js API route (server-side):
// /pages/api/get-data.js
export default async function handler(req, res) {
const data = await fetch('https://api.service.com/data', {
headers: {
'Authorization': `Bearer ${process.env.API_SECRET_KEY}`
}
});
res.json(await data.json());
}
Securing v0 Components for Production
Pre-Production Security Checklist
Review for dangerouslySetInnerHTML usage
Add server-side validation for all form inputs
No API keys or secrets in component code
Check that external links use rel="noopener noreferrer"
Verify data fetching goes through your API routes
Test with malicious input (scripts, SQL, etc.)
Add rate limiting on backend endpoints
Set proper CORS headers on API routes
Integrating v0 Components with Backends
When you connect v0 components to real data, follow these patterns:
Safe Data Fetching
// In your v0 component
'use client';
import { useState, useEffect } from 'react';
export function UserProfile({ userId }) {
const [user, setUser] = useState(null);
useEffect(() => {
// Fetch through your API route, not directly
fetch(`/api/users/${userId}`)
.then(res => res.json())
.then(setUser);
}, [userId]);
// Component renders user data...
}
// Your API route handles auth and validation
// /app/api/users/[id]/route.js
import { getServerSession } from 'next-auth';
export async function GET(request, { params }) {
const session = await getServerSession();
// Check authentication
if (!session) {
return Response.json({ error: 'Unauthorized' }, { status: 401 });
}
// Only allow users to fetch their own data
if (session.user.id !== params.id) {
return Response.json({ error: 'Forbidden' }, { status: 403 });
}
// Fetch from database
const user = await db.users.findOne({ id: params.id });
return Response.json(user);
}
Safe Form Submission
// v0 component with form
export function ContactForm() {
const handleSubmit = async (e) => {
e.preventDefault();
const formData = new FormData(e.target);
// Submit to your API route
const res = await fetch('/api/contact', {
method: 'POST',
body: JSON.stringify(Object.fromEntries(formData)),
headers: { 'Content-Type': 'application/json' }
});
// Handle response...
};
}
// API route with server validation
// /app/api/contact/route.js
import { z } from 'zod';
const schema = z.object({
email: z.string().email(),
message: z.string().min(1).max(1000)
});
export async function POST(request) {
const body = await request.json();
// Server-side validation
const result = schema.safeParse(body);
if (!result.success) {
return Response.json({ error: result.error }, { status: 400 });
}
// Process validated data...
}
v0 vs Full-Stack AI Tools
| Aspect | v0 | Bolt / Lovable |
|---|---|---|
| Output type | UI components only | Full applications |
| Backend included | No | Yes |
| Database setup | You handle it | Often included |
| Auth included | No | Sometimes |
| Security concerns | XSS, data handling | API keys, database, auth |
| Control level | High (you build backend) | Lower (generated backend) |
Is v0 safe to use for production apps?
v0 generates frontend components that are generally safe when used correctly. The security of your app depends on how you integrate these components with your backend. Always add proper authentication, authorization, and input validation on the server side.
Does v0 generate secure code by default?
v0 uses React best practices and avoids obvious security issues. However, it generates UI components, not security logic. You need to add authentication, authorization, and validation yourself when connecting to real data.
Can I use v0 components with sensitive data?
Yes, but never fetch sensitive data directly from the frontend. Always go through authenticated API routes that verify the user has permission to access the data. The v0 component should only display what your backend allows.
Should I review v0 generated code before using it?
Yes. Check for patterns like dangerouslySetInnerHTML, ensure external links have proper rel attributes, and verify there are no hardcoded values that should be environment variables. It only takes a few minutes and prevents issues.