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Authentication and Session Weaknesses — Practical Guide to Common Flaws and Testing

This content explains common authentication and session management vulnerabilities, why they matter, real-world metaphors, technical details, testing checklists, mitigations, and ethical OPSEC guidance for pentesters. It focuses on pragmatic fixes (crypto, cookie flags, session revocation), examples, and how to test responsibly.

Content Overview

Title and Opening Quote

Authentication and Session Weaknesses — The Delightfully Unsexy Ways Apps Let You In "Authentication is the bouncer. Session management is the clipboard that decides which names are legit." — Your friendly neighborhood security TA, caffeinated and slightly dramatic.

Context and Focus

You're coming in hot from OWASP Top 10 and Threat Modeling (we built the map and found the dark alleys already). Now we chase the pickpockets: authentication and session weaknesses. These are low-hanging fruit with high impact — the juicy results everyone wants but few harden well.

Why This Matters

Why this matters (without repeating previous intros): authentication flaws show up in threat models as high-impact, high-likelihood paths to compromise. Session weaknesses are the stealthy persistence mechanisms attackers love — think a golden ticket that never expires.

Chapter Overview (TL;DR)

What's in this chapter (TL;DR) Authentication weaknesses : bad passwords, broken flows, weak reset processes, flighty MFA Session weaknesses : predictable tokens, insecure cookies, token leakage, long-lived sessions Real-world style examples, testing checklist, and ethical OPSEC notes (you...

Anatomy of the Attack (Metaphor)

Anatomy of the attack (a quick greedy chef metaphor) Imagine the app is a restaurant. Authentication = the host checks your reservation. Session = the wristband that says you paid and can access the VIP. Weak auth = fake reservation. Weak session = flimsy wristband you can copy or forge. If rese...

Common Authentication Weaknesses (and Exploits)

Common Authentication Weaknesses (and how attackers exploit them) Broken login logic (authorization/authentication confusion) Example: account lookup only checks username, not password under certain code paths. Attack: craft requests to bypass password checks. Weak credential storage / pass...

Session Weaknesses and Code Examples

Session Weaknesses — The technical cheat codes Predictable tokens : pseudorandomness with low entropy. Tokens in URL : leaked in logs, referer headers. Cookies missing Secure/HttpOnly/SameSite flags JWT pitfalls : alg=none acceptance, missing signature verification, long exp Session fixati...

Quick Testing Checklist for Pentesters

Quick testing checklist for pentesters (ethical, with OPSEC in mind) Enumerate auth endpoints: /login, /auth, /oauth/token, /reset Check error messages for user enumeration Try default creds & credential stuffing (only with permission; throttle!) Inspect cookies and token transport (cook...

Mitigations, History, Ethical OPSEC, and Closing

Table: Weakness vs Example vs Mitigation Weakness Example Mitigation Predictable token session IDs like sess1234 Use crypto-grade RNG, NIST recommendations for entropy Token in URL /app?token=... Send tokens via Secure HttpOnly cookies; remove tokens from GET parameters Missin...

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