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/miru-zero/zero-brain/api-auth-and-jwt-abusenpx skills add miru-zero/zero-brain --skill api-auth-and-jwt-abusegit clone --depth 1 https://github.com/miru-zero/zero-brainWrote 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/miru-zero/zero-brain/api-auth-and-jwt-abuse)<a href="https://agentmods.dev/skills/miru-zero/zero-brain/api-auth-and-jwt-abuse"><img src="https://agentmods.dev/badge/skills/miru-zero/zero-brain/api-auth-and-jwt-abuse.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 5.1 | $0.00041 | $0.00619 |
| Opus 5 | $0.00020 | $0.00309 |
| Sonnet 5 | $0.00008 | $0.00124 |
| Haiku 4.5 | $0.00004 | $0.00062 |
Grade A, and why
api-auth-and-jwt-abuse scanned grade A with 0 findings 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 6d 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
97% identical to api-auth-and-jwt-abuse — 4 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
What it actually says
SKILL: API Auth and JWT Abuse — Token Trust, Header Tricks, and Rate Limits
AI LOAD INSTRUCTION: Use this skill when APIs rely on JWT, bearer tokens, API keys, or weak request identity signals. Focus on token trust boundaries, claim misuse, header spoofing, and rate-limit bypass.
1. TOKEN TRIAGE
Inspect:
alg,kid,jku,x5u- role, org, tenant, scope, or privilege claims
- issuer and audience mismatches
- reuse of mobile and web tokens across products
2. QUICK ATTACK PICKS
| Pattern | First Test |
|---|---|
alg:none acceptance |
unsigned token with trailing dot |
| RS256 confusion | switch to HS256 using public key as secret |
kid lookup trust |
path traversal or injection in kid |
| remote key fetch trust | attacker-controlled jku or x5u |
| weak secret | offline crack with targeted wordlists |
3. HIDDEN FIELDS AND BATCH ABUSE
Mass assignment field picks
role
isAdmin
admin
verified
plan
tier
permissions
org
owner
Rate limit and batch abuse picks
X-Forwarded-For: 1.2.3.4
X-Real-IP: 5.6.7.8
Forwarded: for=9.9.9.9
GraphQL or JSON batch abuse candidates:
- arrays of login mutations
- bulk object fetches with varying IDs
- repeated password reset or verification calls in one request
4. RATE LIMIT BYPASS FAMILIES
X-Forwarded-For
X-Real-IP
Forwarded
User-Agent rotation
Path case / slash variants
5. NEXT ROUTING
- For GraphQL batching and hidden parameters: graphql and hidden parameters
- For default credential and brute-force planning: authentication bypass
- For full JWT and OAuth depth: jwt oauth token attacks
- For OAuth or OIDC configuration flaws in browser and SSO flows: oauth oidc misconfiguration
- For credentialed browser reads and origin trust bugs: cors cross origin misconfiguration
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.
- 6d ago First seen · 76 lines · 41 tokens per session scan A fc833087f011
api-auth-and-jwt-abuse is a skill published in the GitHub repository miru-zero/zero-brain (0 stars, last pushed 19d ago), licensed MIT. It adds 41 tokens to every session and 619 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to api-auth-and-jwt-abuse, differing in 4 lines, and is treated as a copy.
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