How to Fix Auth Middleware Bypass in AI-Built Apps

Authentication middleware can be bypassed, exposing protected routes. AI-generated auth checks often have logic gaps that allow unauthenticated access to sensitive endpoints.

Error messages you might see

Error: Unauthorized access detected on protected route
Warning: Auth middleware did not run for request path /api/admin

Why this happens in AI-generated code

1

Incomplete route matching

Middleware only checks exact paths, missing nested routes like /api/admin/users or routes with query params.

2

Missing method checks

AI code checks auth on GET requests but forgets to protect POST, PUT, or DELETE on the same endpoint.

3

Early return before auth check

Middleware has conditional logic that returns a response before the authentication check runs.

How to fix it

1

Use allowlist instead of blocklist

Protect all routes by default and explicitly allow public routes, rather than trying to block individual protected ones.

2

Apply auth at multiple layers

Check authentication in both middleware and individual route handlers as defense in depth.

3

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Frequently asked questions

How do I test for auth bypass vulnerabilities?

Try accessing protected routes without tokens, with expired tokens, and with tokens from different users. Test all HTTP methods.

Should I check auth in middleware or route handlers?

Both. Middleware provides a first line of defense, and route-level checks ensure protection even if middleware is misconfigured.

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