Authentication — Complete Deep Dive

A detailed guide to PortSwigger authentication labs, which teach how websites verify users and protect logged-in features.

In plain words
What is it for?
BSCP preparation, bug-bounty learning, and understanding issues such as username discovery, two-factor bypasses, password-reset flaws, and related exploit chains.
Why use it?
It gives structured examples for studying common authentication mistakes and practicing security testing in lab environments.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/shulkwisec/bb-huge/authentication
Any agent
npx skills add ShulkwiSEC/bb-huge --skill authentication
Clone the repo
git clone --depth 1 https://github.com/ShulkwiSEC/bb-huge

Made for: Claude Code, Codex.

Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,439 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00025 $0.01439
Opus 5 $0.00013 $0.00720
Sonnet 5 $0.00005 $0.00288
Haiku 4.5 $0.00003 $0.00144

Measured 2d ago against content hash f58b2f397942, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Authentication — Complete Deep Dive scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/process.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

tools: [burp-suite, curl, sqlmap, ffuf, python, hashcat, ysoserial]
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

skills/curated/authentication/SKILL.md · 168 lines

How it starts

The opening of the file, as written. The whole thing — 168 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Authentication — Complete Deep Dive

Deep-Dive Lab Playbook — Every PortSwigger lab variant with exact payloads, bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert

When to Use

  • BSCP certification prep
  • Real-world bug bounty hunting
  • Building exploitation chains
  • Understanding bypass techniques

Prerequisites

  • Burp Suite Professional
  • Burp Collaborator / interactsh
  • Browser with proxy configured

Workflow

Phase 1: Reconnaissance

  • Identify input vectors, parameters, and application behavior.

Phase 2: Exploitation

  • Apply standard lab payloads.

Phase 3: Zero-Day Escalation

  • Fuzz filters, bypass WAFs, and chain with other vulns.

Lab Playbooks

Lab 1: Username enum different responses 🟢 APPRENTICE

Burp Intruder with username wordlist. Check response length/content difference: Invalid username vs Incorrect password.

Lab 2: 2FA simple bypass 🟢 APPRENTICE

After login, skip /login2 (2FA page) and navigate directly to /my-account.

Lab 3: Password reset broken logic 🟢 APPRENTICE

POST /forgot-password?temp-forgot-password-token=TOKEN HTTP/1.1

temp-forgot-password-token=TOKEN&username=carlos&new-password-1=hacked&new-password-2=hacked

Change username to victim. Token validation doesn't check user ownership.

Lab 4: Subtly different responses 🟡 PRACTITIONER

Check for trailing period: Invalid username or password vs Invalid username or password.

Lab 5: Response timing 🟡 PRACTITIONER

Long password → longer response time for valid usernames (bcrypt hash computed). Use X-Forwarded-For: 1.1.1.§1§ to bypass IP lock.

Lab 6: Broken brute-force IP block 🟡 PRACTITIONER

Login with valid creds every 2 attempts to reset the IP counter. Alternate: valid→attack→valid→attack.

Lab 7: Username enum via account lock 🟡 PRACTITIONER

Locked account = account exists. Send 5 attempts for each username. Locked response = valid user.

Read the full file on GitHub · 168 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 168 lines · 25 tokens per session scan A f58b2f397942

Subscribe to this mod's changes

Authentication — Complete Deep Dive is a skill published in the GitHub repository ShulkwiSEC/bb-huge (21 stars, last pushed 1mo ago), licensed MIT. It adds 25 tokens to every session and 1,439 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.