Don't Roll Your Own Crypto
Authentication is hard. Use standards. One of the most common mistakes in 2026 is confusing OAuth2 (Authorization) with OpenID Connect (Authentication). OAuth2 is about giving a valet key (Access Token) to park your car. OIDC is about verifying the driver's license (ID Token).
The JWT Controversy
JSON Web Tokens (JWT) are a popular stateless authentication mechanism. However, they come with significant risks if mishandled:
- Storage: Never store JWTs in
localStorage. Any XSS vulnerability gives attackers full access to your user's account. Always useHttpOnly,Securecookies. - Revocation: Since JWTs are stateless, you can't 'delete' them on the server to log a user out. You must wait for them to expire. This is why short expiry times (e.g., 15 minutes) combined with Refresh Tokens are critical.
- Algorithm Confusion: Ensure your verification library explicitly checks the algorithm (e.g., RS256) and doesn't allow the 'None' algorithm attack.
Conclusion
Security is nuanced. By sticking to established protocols like OIDC and storing tokens securely in cookies, you protect your users from 99% of identity attacks.