Security for Auth-Heavy Applications
Apps with complex authentication — OAuth, MFA, role hierarchies, SSO — have the widest attack surface for identity-related exploits. AI-generated auth code is where the most critical vulnerabilities occur.
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Why Security Matters for Authentication-Heavy Applications
Authentication is the gateway to everything. A flaw in your auth system compromises all other security measures. AI tools generate auth flows that look correct but have subtle vulnerabilities: missing CSRF tokens in OAuth, insecure token storage, predictable reset tokens, and broken role checks. The complexity of modern auth (OAuth + MFA + SSO + role hierarchies) means AI tools almost never generate a complete, secure implementation.
Security Risks
OAuth state parameter missing
criticalOAuth flows without CSRF protection via the state parameter, allowing login CSRF attacks.
Mitigation
Always include a random, unguessable state parameter in OAuth authorization requests. Verify it matches when handling the callback.
Insecure token storage
highJWT tokens stored in localStorage, accessible to XSS attacks.
Mitigation
Store tokens in HttpOnly cookies. If using localStorage, ensure your CSP prevents XSS. Use short-lived access tokens with refresh token rotation.
Broken role escalation
highUsers able to modify their own role or access role-restricted resources by manipulating requests.
Mitigation
Store roles server-side. Never trust role claims from the client. Check authorization on every request against the server-side role.
Security Checklist
CSRF protection on all OAuth flows using random state values.
HttpOnly cookies for session tokens. Short-lived JWTs with refresh rotation.
Check permissions on every request against server-stored roles, not client claims.
Minimum length, complexity requirements, and breach database checks.
Lock accounts after repeated failed login attempts.
Allow users to log out of all sessions. Invalidate sessions on password change.
Real-World Scenario
A developer builds a B2B app with Google OAuth using Bolt. The AI-generated OAuth callback doesn't validate the state parameter. An attacker crafts a malicious link that initiates an OAuth flow with the attacker's Google account but sends the callback to the victim's session. The victim clicks the link, and the attacker's Google account is now linked to the victim's app account, giving the attacker full access.
Frequently Asked Questions
Should I build my own auth or use a service?
Use a service. Supabase Auth, Firebase Auth, Clerk, or Auth0 handle the hard parts — password hashing, token management, MFA, OAuth — with battle-tested code. Building custom auth introduces vulnerabilities that services have already solved.
Is localStorage safe for JWT tokens?
It's vulnerable to XSS. Any script running on your page can read localStorage. HttpOnly cookies are safer because JavaScript can't access them. If you must use localStorage, ensure you have a strict CSP preventing script injection.
How do I implement role-based access correctly?
Store roles in a server-side database, not in JWT claims or client state. On every request, look up the user's role from the database and check if it permits the requested action. Never trust role information sent from the client.
Security for Other Use Cases
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