Broken Authentication in Windsurf Apps
Windsurf's Cascade agent generates polished authentication flows with login forms, protected routes, and role-based UI rendering. But the authorization logic lives entirely in the frontend, meaning attackers bypass it by calling backend APIs directly.
Scan Your Windsurf AppHow It Happens
Windsurf generates authentication using popular providers like Supabase Auth, Firebase Auth, or NextAuth. The sign-up and login flows work correctly. The problem is what happens after authentication: Cascade implements access control by conditionally rendering React components rather than enforcing permissions at the API or database layer. A typical Windsurf pattern is a middleware file that checks for a session cookie and redirects unauthenticated users to /login. This protects pages but not API routes. The API endpoints that serve data to those pages remain accessible to anyone who sends a request directly, bypassing the middleware entirely. Windsurf also generates role fields stored in user-editable database tables without proper RLS protection. An attacker who can update their own profile row can change their role from "user" to "admin" and gain access to every administrative feature the frontend conditionally renders.
Impact
Broken authorization in Windsurf apps allows privilege escalation. Regular users can access admin dashboards, modify other users' data, and perform actions reserved for higher permission levels by calling the underlying API directly. In multi-tenant Windsurf applications, broken auth can expose data across organizational boundaries. If the API does not verify that the requesting user belongs to the same tenant as the requested data, any authenticated user can access any tenant's resources. Because Windsurf generates professional-looking auth flows, developers and stakeholders assume the app is secure. This false confidence means broken authorization vulnerabilities persist longer and are discovered later, often by attackers rather than developers.
How to Detect
Create two user accounts with different roles. Use the lower-privilege account's session token to call API endpoints that serve admin-only data. If the API returns the data, server-side authorization is missing. Inspect the Windsurf-generated middleware and API route handlers. Look for authorization checks. If route handlers only check that a session exists (isAuthenticated) but not what the user is allowed to do (hasPermission), authorization is broken. Vibe App Scanner tests API endpoints with varying authentication contexts and reports which endpoints lack proper access control, distinguishing between authentication (is the user logged in) and authorization (is the user allowed this action).
How to Fix
Add authorization checks to every API route handler. Each endpoint should verify not just that the user is authenticated, but that they have permission to perform the requested action on the requested resource. For Supabase backends, implement RLS policies that enforce row-level ownership and role-based access. For custom APIs, create middleware that validates user roles from a trusted source (JWT claims or a protected database table). Store user roles in JWT custom claims or in a database table protected by RLS that only allows role changes through admin-only server functions. Never store roles in a table that users can modify through the frontend. Implement rate limiting on login endpoints to prevent credential stuffing. Add account lockout after repeated failed attempts and require email verification for new accounts.
Code Examples
API route authorization in Next.js
// Windsurf-generated API route - no authorization
export async function GET(req: Request) {
const session = await getSession(req)
if (!session) return new Response('Unauthorized', { status: 401 })
// Returns ALL users - no role check
const users = await db.select().from(usersTable)
return Response.json(users)
}// API route with proper authorization
export async function GET(req: Request) {
const session = await getSession(req)
if (!session) return new Response('Unauthorized', { status: 401 })
// Verify admin role from trusted source
const userRole = await db.select({ role: usersTable.role })
.from(usersTable)
.where(eq(usersTable.id, session.user.id))
if (userRole[0]?.role !== 'admin') {
return new Response('Forbidden', { status: 403 })
}
const users = await db.select().from(usersTable)
return Response.json(users)
}Frequently Asked Questions
Does Windsurf generate server-side auth checks?
Windsurf generates authentication (login/signup) correctly, but authorization (access control) is typically implemented only in the UI through conditional rendering and client-side middleware. Server-side enforcement must be added manually.
Is NextAuth/Auth.js sufficient for securing a Windsurf app?
NextAuth handles authentication well but does not provide authorization. You still need to verify user permissions in every API route and database query. NextAuth confirms who the user is; you must decide what they can do.
How can I test if my Windsurf app has broken authentication?
Use a tool like curl or Postman to call your API endpoints directly with a regular user's session token. Try accessing admin-only endpoints and other users' data. If the API returns data it shouldn't, authorization is broken.
Related Security Resources
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