jwt-attack

jwt-attack is a skill for Claude Code, Codex from jinyimeng01/mastermind-bug-bounty. It costs 79 tokens per session (4,565 once invoked), scanned B, original, no licence file.

A guide to testing JWTs (JSON Web Tokens), which are signed strings used to carry login and permission information between services. It covers weak signatures, altered claims, unsafe headers, and token reuse.

In plain words
What is it for?
Use it to review bearer handling, signing algorithms, secrets, key lookup headers, JWKS endpoints, claims, and tokens shared across services.
Why use it?
It helps find mistakes that could let someone change their role, bypass authentication, forge a token, or use one service's token elsewhere.

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/jinyimeng01/mastermind-bug-bounty/jwt_attack
Any agent
npx skills add jinyimeng01/mastermind-bug-bounty --skill jwt_attack
Clone the repo
git clone --depth 1 https://github.com/jinyimeng01/mastermind-bug-bounty

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for jwt-attack

README.md
[![agentmods](https://agentmods.dev/badge/skills/jinyimeng01/mastermind-bug-bounty/jwt_attack.svg)](https://agentmods.dev/skills/jinyimeng01/mastermind-bug-bounty/jwt_attack)
Your own site
<a href="https://agentmods.dev/skills/jinyimeng01/mastermind-bug-bounty/jwt_attack"><img src="https://agentmods.dev/badge/skills/jinyimeng01/mastermind-bug-bounty/jwt_attack.svg" alt="Measured on agentmods" height="20"></a>
Per session 79 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,565 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. Scan, not verified.
Origin unknown 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 $0.00079 $0.04565
Opus 5 $0.00039 $0.02282
Sonnet 5 $0.00016 $0.00913
Haiku 4.5 $0.00008 $0.00456

Measured 5d ago against content hash 4a132a1c47e8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

jwt-attack scanned grade B with 2 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 5d 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.

Downloads and executes remote codemediumSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

curl -s https://target/.well-known/jwks.json | python -m json.tool

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

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

├── Bearer 移除: 5秒,纯 curl
skills/jwt_attack/SKILL.md · 502 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 5d ago First seen · 502 lines · 79 tokens per session scan B 4a132a1c47e8

Subscribe to this mod's changes

jwt-attack is a skill published in the GitHub repository jinyimeng01/mastermind-bug-bounty (57 stars, last pushed 2mo ago), with no licence file. It adds 79 tokens to every session and 4,565 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Related

Other skills, from other repositories

systematic-debugging

Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.

obra/superpowers · 21 tokens

local-ai-agents

Build local-first AI agents that run entirely on a developer workstation with Microsoft Foundry Local and Qwen function-calling models. Covers Small Language Models (SLMs), the OpenAI-compatible local endpoint, sandboxed local tools, local RAG with Chroma, local MCP servers, hybrid cloud/local routing, and the…

microsoft/ai-agents-for-beginners · 200 tokens

next-cache-components-adoption

Turn on Cache Components in a Next.js app and resolve the blocking routes it surfaces. Use when the user wants to enable, adopt, or migrate to Cache Components, flip the cacheComponents flag, work through a flood of blocking-prerender / instant validation errors, run the cache-components-instant-false codemod, or…

vercel/next.js · 95 tokens

insight-error-page

Write or audit an insight-kind error page for the Next.js dev overlay. Use when creating a new errors/ .mdx page, auditing an existing one, or checking that a page matches the framework fix cards. Covers page structure, title alignment, FixCard cards with Copy prompt button, code snippets, terminology verification…

vercel/next.js · 83 tokens

next-cache-components-optimizer

Drive a Next.js route to instant navigation by setting up an agentic loop, under Cache Components / PPR, on initial load (hard navigation) and client-side navigation (soft navigation). Encode the goal as a failing @next/playwright instant() e2e and work it to green, one verified route at a time; the shipped test then…

vercel/next.js · 170 tokens

next-partial-prefetching-adoption

Turn on Partial Prefetching in a Next.js app and work through the insights it surfaces. Use when the user wants to enable or adopt Partial Prefetching, flip the partialPrefetching flag, opt routes in with export const prefetch = 'partial', audit Link prefetch={true} behavior, preserve existing prefetched UI with…

vercel/next.js · 103 tokens