jwt-oauth

jwt-oauth is a skill for Claude Code, Codex from sanjaysaini1952/BugBounty-Arsenal. It costs 0 tokens per session (750 once invoked), scanned A, original, MIT.

A security-testing guide for JWT and OAuth authentication. JWTs are signed tokens used to carry identity claims, while OAuth is a standard for delegated login and access.

In plain words
What is it for?
Use it to test token algorithms, signatures, claims, expiration, key lookup, embedded key sources, and OAuth redirect handling.
Why use it?
It helps find authentication flaws such as accepting altered or expired tokens, trusting unsafe signing settings, weak secrets, or insecure OAuth redirects.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to test token algorithms, signatures, claims, expiration, key lookup, embedded key sources, and OAuth redirect handling.

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Install with agentmods
npx agentmods add skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth
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.

Any agent
npx skills add sanjaysaini1952/BugBounty-Arsenal --skill jwt-oauth
Clone the repo
git clone --depth 1 https://github.com/sanjaysaini1952/BugBounty-Arsenal

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-oauth

README.md
[![agentmods](https://agentmods.dev/badge/skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth/github.svg)](https://agentmods.dev/skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth)
Your own site
<a href="https://agentmods.dev/skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth"><img src="https://agentmods.dev/badge/skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth/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.

agentmods 80×15 button for jwt-oauth

Your own site · 80×15
<a href="https://agentmods.dev/skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth"><img src="https://agentmods.dev/badge/skills/sanjaysaini1952/bugbounty-arsenal/jwt-oauth.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 750 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00000 $0.00750
Opus 5 $0.00000 $0.00375
Sonnet 5 $0.00000 $0.00150
Haiku 4.5 $0.00000 $0.00075

Measured 12d ago against content hash 7e651bf39da6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

jwt-oauth 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 12d 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.

skills/hunting/jwt-oauth/SKILL.md · 79 lines

How it starts

The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.

JWT / OAuth Security Testing Skill — 8+8 Test Cases

Load when: JWT, OAuth, SSO, token security, authentication.

172. JWT alg:none attack (easy)

Decode JWT, change "alg": "RS256" to "alg": "none", remove signature. Submit token. Report if accepted.

173. JWT key confusion (medium)

If app uses RS256, sign token with HMAC using public key. Report if accepted.

174. JWT secret brute force (medium)

If JWT uses HS256 with weak secret, brute force with common passwords. Use jwt_tool.

175. JWT expired token acceptance (easy)

Use expired JWT token. Report if expiration is validated.

176. JWT claim manipulation (medium)

Modify sub, role, isAdmin, exp claims in JWT. Report if modifications are accepted.

177. JWT kid injection (medium)

If JWT has "kid" parameter, inject: {"kid": "/dev/null"} or {"kid": "../../dev/null"}. Report path traversal in key lookup.

178. JWT jwk/jku confusion (hard)

If app validates JWT via embedded JWK or JWKS URL, inject attacker's public key or URL.

179. JWT none algorithm + key confusion combined (hard)

Combine alg:none bypass with claim manipulation for full auth bypass.

180. OAuth redirect_uri open redirect (hard)

If OAuth validates redirect_uri loosely, test subdomain tricks, path traversal, URL parser confusion.

181. OAuth state parameter missing (medium)

Remove state parameter from OAuth flow. Report CSRF vulnerability.

182. OAuth token leakage via referrer (medium)

Check if OAuth tokens appear in URLs that get sent via Referer header.

183. OAuth token leakage via logs (medium)

Check if access tokens appear in server logs, CDN logs, analytics.

184. OAuth scope escalation (medium)

Request elevated scopes beyond what app needs. Report if excessive scopes are granted.

185. OAuth token replay (medium)

Use OAuth refresh token after it should be invalidated (password change, logout).

186. OAuth PKCE bypass (hard)

If app uses PKCE, test if code_verifier check is enforced or can be bypassed.

Read the full file on GitHub · 79 lines

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. 12d ago First seen · 79 lines · 0 tokens per session scan A 7e651bf39da6

Subscribe to this mod's changes

jwt-oauth is a skill published in the GitHub repository sanjaysaini1952/BugBounty-Arsenal (2 stars, last pushed 1mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 750 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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