v0 Security Incidents
AI-generated code vulnerabilities in v0 output: XSS, missing validation, hardcoded values, and insecure patterns.
Not v0 platform bugs, but the security quality of the code it generates. What to review and fix before deploying v0-generated components to production.
VAS checks for XSS, exposed keys, missing headers, and authentication issues
About This Page
v0 by Vercel is an AI-powered tool that generates React and Next.js components from text prompts. It produces high-quality UI code and is excellent for rapid prototyping. The security issues documented here are not bugs in v0 itself but rather patterns in the generated output that require human review before production deployment. This is consistent with all AI code generation tools.
Understanding v0's Security Surface
v0 occupies a unique position in the vibe coding ecosystem. Unlike full-stack tools like Lovable or Bolt.new that generate entire applications with backends, databases, and deployment configurations, v0 focuses primarily on generating frontend React and Next.js components. This means its security surface is different and in many ways smaller than its full-stack counterparts.
You will not find Supabase RLS misconfigurations or exposed database credentials in typical v0 output. Instead, the security concerns center on client-side vulnerabilities: cross-site scripting (XSS) vectors, missing input validation, hardcoded configuration values, client-side-only authentication checks, and insecure data fetching patterns.
These issues may seem less severe than a fully exposed database, but they can still lead to serious security incidents. XSS vulnerabilities allow attackers to steal session tokens and user data. Missing input validation enables injection attacks. Client-side auth checks provide no actual security. And when developers extend v0 output to build full applications, the insecure patterns in the generated foundation propagate throughout the entire codebase.
The security quality of v0's output has improved over time. Vercel has invested in making the generated code more secure by default. However, security is contextual; it depends on how the generated code is used, what data it handles, and what modifications developers make after generation. This page documents the patterns that require attention regardless of v0's improvements.
Security Vulnerability Patterns
Cross-Site Scripting via dangerouslySetInnerHTML
v0 generates components that use React's dangerouslySetInnerHTML to render rich text content, markdown previews, or HTML from APIs. While sometimes necessary, this bypasses React's built-in XSS protections. When user-generated content flows into these components, it creates a direct XSS vector.
Vulnerable Pattern
// v0-generated component for rendering blog content
function BlogPost({ post }) {
return (
<article>
<h1>{post.title}</h1>
{/* XSS vulnerability if post.content contains malicious HTML */}
<div dangerouslySetInnerHTML={{ __html: post.content }} />
</article>
)
}Secure Pattern
// Fixed: Sanitize HTML before rendering
import DOMPurify from 'dompurify'
function BlogPost({ post }) {
const sanitizedContent = DOMPurify.sanitize(post.content)
return (
<article>
<h1>{post.title}</h1>
<div dangerouslySetInnerHTML={{ __html: sanitizedContent }} />
</article>
)
}Missing Input Validation on Forms
v0 generates visually appealing forms with proper styling and labels but frequently omits input validation beyond basic HTML5 attributes. Server-side validation is almost never generated. This leaves applications vulnerable to injection attacks, data corruption, and business logic bypasses.
Vulnerable Pattern
// v0-generated contact form - no validation
export function ContactForm() {
async function handleSubmit(formData: FormData) {
'use server'
const name = formData.get('name')
const email = formData.get('email')
const message = formData.get('message')
// Directly passed to database/email without validation
await db.insert({ name, email, message })
}
return (
<form action={handleSubmit}>
<input name="name" placeholder="Name" />
<input name="email" placeholder="Email" />
<textarea name="message" placeholder="Message" />
<button type="submit">Send</button>
</form>
)
}Secure Pattern
// Fixed: Proper validation with Zod
import { z } from 'zod'
const contactSchema = z.object({
name: z.string().min(1).max(100).trim(),
email: z.string().email().max(254),
message: z.string().min(10).max(5000).trim(),
})
export function ContactForm() {
async function handleSubmit(formData: FormData) {
'use server'
const result = contactSchema.safeParse({
name: formData.get('name'),
email: formData.get('email'),
message: formData.get('message'),
})
if (!result.success) {
return { error: result.error.flatten() }
}
await db.insert(result.data)
}
// ... form JSX with client-side validation too
}Hardcoded Configuration Values and API Keys
When generating full-page components that integrate with services, v0 often includes placeholder or actual API keys, URLs, and configuration values directly in the component code. These end up in the client-side bundle and are visible to anyone inspecting the page source.
Vulnerable Pattern
// v0-generated component with hardcoded values
const STRIPE_KEY = "pk_live_51H..." // Real Stripe key
const API_URL = "https://api.myapp.com" // Internal API URL
const MAPS_KEY = "AIzaSy..." // Google Maps key
export function PaymentForm() {
// Uses hardcoded Stripe key directly
const stripe = loadStripe(STRIPE_KEY)
// ...
}Secure Pattern
// Fixed: Use environment variables
export function PaymentForm() {
const stripe = loadStripe(
process.env.NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY!
)
// Only NEXT_PUBLIC_ prefixed vars are in client bundle
// Server-side secrets stay on the server
}Client-Side Only Authentication Checks
v0 generates authentication UI with conditional rendering based on client-side state. The generated code checks whether a user is logged in on the client but does not enforce authentication on the server. An attacker can bypass these checks by modifying JavaScript or directly accessing API endpoints.
Vulnerable Pattern
// v0-generated dashboard with client-side auth check
'use client'
import { useUser } from '@/hooks/use-user'
export function AdminDashboard() {
const { user, isLoading } = useUser()
if (isLoading) return <div>Loading...</div>
if (!user) return <div>Not authorized</div>
// This "protection" only hides the UI
// The API endpoints and data are still accessible
return (
<div>
<h1>Admin Dashboard</h1>
{/* Admin content rendered client-side */}
</div>
)
}Secure Pattern
// Fixed: Server-side auth check in Next.js
import { auth } from '@/lib/auth'
import { redirect } from 'next/navigation'
export default async function AdminDashboard() {
const session = await auth()
if (!session?.user) {
redirect('/login')
}
if (session.user.role !== 'admin') {
redirect('/unauthorized')
}
// Data fetched server-side with auth
const data = await getAdminData(session.user.id)
return (
<div>
<h1>Admin Dashboard</h1>
{/* Content rendered with server-verified auth */}
</div>
)
}JavaScript Protocol in href Attributes
v0 occasionally generates components where user-controlled values flow into href attributes without sanitization. This can allow javascript: protocol injection, enabling XSS attacks. This is particularly common in components that render lists of links, user profiles with website URLs, or dynamic navigation items.
Vulnerable Pattern
// v0-generated user profile with link
function UserProfile({ user }) {
return (
<div>
<h2>{user.name}</h2>
{/* XSS if user.website = "javascript:alert(document.cookie)" */}
<a href={user.website}>Visit Website</a>
</div>
)
}Secure Pattern
// Fixed: Validate URL protocol
function UserProfile({ user }) {
const safeUrl = user.website &&
(user.website.startsWith('https://') || user.website.startsWith('http://'))
? user.website
: '#'
return (
<div>
<h2>{user.name}</h2>
<a href={safeUrl} rel="noopener noreferrer" target="_blank">
Visit Website
</a>
</div>
)
}Missing CSRF Protection on Form Actions
v0 generates forms with server actions or API calls but does not include CSRF tokens or other cross-site request forgery protections. While Next.js Server Actions have some built-in CSRF protection through origin checking, traditional form submissions and custom API routes may be vulnerable.
Vulnerable Pattern
// v0-generated form without CSRF protection
export function UpdateProfile() {
return (
<form method="POST" action="/api/profile/update">
<input name="name" defaultValue={user.name} />
<input name="email" defaultValue={user.email} />
<button type="submit">Update</button>
{/* No CSRF token - vulnerable to cross-site submission */}
</form>
)
}Secure Pattern
// Fixed: Use Server Actions (built-in CSRF) or add token
// Option 1: Next.js Server Actions (recommended)
export function UpdateProfile() {
async function updateProfile(formData: FormData) {
'use server'
// Server Actions include origin checking
const session = await auth()
if (!session) throw new Error('Unauthorized')
// ... validate and update
}
return <form action={updateProfile}>...</form>
}
// Option 2: For API routes, add CSRF token
import { generateCSRFToken, validateCSRFToken } from '@/lib/csrf'Unauthenticated API Route Handlers
When v0 generates Next.js API routes or Server Actions, it frequently creates endpoints that accept and process requests without verifying the caller's identity. These routes are publicly accessible and can be called by anyone with the URL.
Vulnerable Pattern
// v0-generated API route - no auth check
// app/api/users/route.ts
export async function GET() {
const users = await db.select().from(usersTable)
return Response.json(users) // Returns ALL users to anyone
}
export async function DELETE(req: Request) {
const { userId } = await req.json()
await db.delete(usersTable).where(eq(usersTable.id, userId))
return Response.json({ success: true }) // Anyone can delete users
}Secure Pattern
// Fixed: Auth check on every route
import { auth } from '@/lib/auth'
export async function GET() {
const session = await auth()
if (!session) {
return Response.json({ error: 'Unauthorized' }, { status: 401 })
}
// Only return current user's data
const user = await db.select().from(usersTable)
.where(eq(usersTable.id, session.user.id))
return Response.json(user)
}
export async function DELETE(req: Request) {
const session = await auth()
if (!session || session.user.role !== 'admin') {
return Response.json({ error: 'Forbidden' }, { status: 403 })
}
// ... admin-only operations with audit logging
}v0 Security vs Other AI Code Tools
| Security Aspect | v0 | Lovable | Bolt.new |
|---|---|---|---|
| Primary risk | Client-side XSS | RLS/auth issues | Exposed credentials |
| Database exposure risk | Low (frontend focus) | High | High |
| XSS risk | Medium | Medium | Medium |
| Input validation | Often missing | Often missing | Often missing |
| Security headers | Via Vercel defaults | Usually missing | Usually missing |
| Auth implementation | Client-side only | Supabase Auth | Varies |
v0 Security Review Checklist
Before Deploying v0 Code
- Search for dangerouslySetInnerHTML and add sanitization
- Add server-side validation for all form inputs
- Move hardcoded values to environment variables
- Add authentication checks to API routes and server actions
- Verify href attributes do not accept user input unsanitized
- Check for client-side-only auth that needs server enforcement
After Deploying
- Run a security scan on the deployed URL
- Verify security headers are properly configured
- Test authentication by accessing protected routes directly
- Check browser console for exposed configuration
- Test input fields with special characters and HTML
- Verify error messages do not expose internal details
Scan Your v0-Built Application
VAS checks for XSS vectors, missing security headers, exposed credentials, and authentication issues in deployed Next.js applications. Get a comprehensive report in minutes.
Frequently Asked Questions
Is v0 safe to use for production applications?
v0 generates high-quality UI components and is excellent for prototyping and building interfaces. However, the generated code should be treated as a starting point, not production-ready code. v0 primarily generates frontend components using React and Next.js, and its output typically lacks server-side security controls, input validation, proper error handling, and authentication patterns. For production use, always review generated code for XSS vectors, add server-side validation, implement proper authentication, and run a security scan before deploying.
What security vulnerabilities does v0 commonly generate?
The most common security issues in v0-generated code include: 1) Cross-site scripting (XSS) vectors from using dangerouslySetInnerHTML or rendering unsanitized user input, 2) Missing input validation on forms and user input fields, 3) Hardcoded API keys and configuration values, 4) Client-side only validation without server-side enforcement, 5) Missing CSRF protection on form submissions, 6) Insecure data fetching patterns that expose sensitive information in client-side code.
Does v0 generate code with XSS vulnerabilities?
v0 can generate code with XSS vulnerabilities, particularly when handling dynamic content. React's JSX generally escapes content by default, which provides base-level XSS protection. However, v0 may generate code that uses dangerouslySetInnerHTML for rendering rich content, bypasses React's escaping for specific use cases, or renders user input in href attributes. The risk increases when developers modify v0 output to add dynamic content rendering.
How is v0 different from Lovable or Bolt for security?
v0 focuses primarily on frontend UI component generation (React/Next.js), while Lovable and Bolt generate full-stack applications including backend logic, database connections, and authentication. This means v0's security surface is smaller - it does not typically generate database configurations, API routes, or auth systems. However, v0's frontend focus means more subtle client-side vulnerabilities like XSS and improper state management.
Should I scan v0-generated code before deploying?
Yes, absolutely. Even though v0 generates primarily frontend components, the deployed application can still have security issues including missing security headers, XSS vectors, exposed configuration values, and insecure data fetching patterns. VAS is particularly effective for v0 projects because it scans the deployed application and checks for runtime security issues common in AI-generated Next.js applications.
Last updated: February 2026