attacking-oauth-oidc

attacking-oauth-oidc is a skill for Claude Code from trilwu/secskills. It costs 182 tokens per session (4,174 once invoked), scanned A, original, MIT.

A security-testing guide for OAuth 2.0 and OpenID Connect, the standards behind many “Sign in with” buttons and delegated access. It examines how authorization codes, tokens, redirects, and browser callbacks are handled.

In plain words
What is it for?
Use it to test authorization endpoints, callback URLs, redirect URI checks, state, PKCE, scopes, discovery documents, and code-to-token exchanges.
Why use it?
It helps uncover unsafe redirect handling and missing protections that could expose login codes, tokens, or user sessions.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the secskills-offense plugin — 40 skills shipped together

Good fit Use it to test authorization endpoints, callback URLs, redirect URI checks, state, PKCE, scopes, discovery documents, and code-to-token exchanges.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/trilwu/secskills/attacking-oauth-oidc
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 trilwu/secskills --skill attacking-oauth-oidc
Clone the repo
git clone --depth 1 https://github.com/trilwu/secskills

Made for: Claude Code.

Or install secskills-offense, the plugin that ships this one along with the rest of its 40 skills.

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 attacking-oauth-oidc

README.md
[![agentmods](https://agentmods.dev/badge/skills/trilwu/secskills/attacking-oauth-oidc/github.svg)](https://agentmods.dev/skills/trilwu/secskills/attacking-oauth-oidc)
Your own site
<a href="https://agentmods.dev/skills/trilwu/secskills/attacking-oauth-oidc"><img src="https://agentmods.dev/badge/skills/trilwu/secskills/attacking-oauth-oidc/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 attacking-oauth-oidc

Your own site · 80×15
<a href="https://agentmods.dev/skills/trilwu/secskills/attacking-oauth-oidc"><img src="https://agentmods.dev/badge/skills/trilwu/secskills/attacking-oauth-oidc.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 182 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,174 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 6 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Privilege Escalation · line 36
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high YARA Match · line 41
    YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).
    Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.
  • high Prompt Injection · line 336
    Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.
    Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
  • high Privilege Escalation · line 346
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • medium Excessive Agency · line 3
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
  • medium Excessive Agency · line 225
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
How audits are shown
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 $0.00182 $0.04174
Opus 5 $0.00091 $0.02087
Sonnet 5 $0.00036 $0.00835
Haiku 4.5 $0.00018 $0.00417

Measured 5d ago against content hash 4373ba057c46, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

attacking-oauth-oidc 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 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.

Makes network callslowCapability

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

curl -s https://target/.well-known/openid-configuration | jq .
secskills-offense/skills/attacking-oauth-oidc/SKILL.md · 367 lines

How it starts

The opening of the file, as written. The whole thing — 367 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Attacking OAuth and OIDC

OAuth is a delegation protocol whose security lives entirely in parameters the browser forwards — redirect_uri, state, and scope — so most breaks are the authorization server or the client trusting one of those a little too much. The token is the prize; the flow is the attack surface. Follow the redirect that carries the code, and you follow the credential.

Only against systems you are authorized to test.

When to Use

  • A login page offers "Sign in with Google / Microsoft / GitHub / Apple" or any federated identity button
  • You see /authorize, /oauth/token, /oauth2/authorize, or a callback URL carrying code=, state=, or #access_token=
  • Requests contain response_type, redirect_uri, client_id, scope, or nonce
  • An OIDC discovery document is served at /.well-known/openid-configuration
  • The app exchanges an authorization code server-side for tokens, or accepts an id_token to establish a session
  • A first-party SPA or mobile app runs the authorization-code-with-PKCE flow

When NOT to Use

  • Forging, cracking, or tampering with the issued token itself (alg confusion, kid injection, weak HMAC secret, none) — use attacking-jwt
  • General web application testing unrelated to the auth flow — use testing-web-applications
  • The resource API after you already hold a valid access token — use testing-apis
  • Entra/Azure AD tenant consent, app registration abuse, and multi-tenant app attacks specifically — use attacking-entra-id
  • The human side — running consent-phishing or illicit-grant campaigns at scale against real users — use performing-social-engineering

Enumerate the Server: Discovery Document First

The OIDC discovery document hands you the entire attack map — every endpoint, the supported flows, and the key set.

curl -s https://target/.well-known/openid-configuration | jq .
# Also try, per-tenant / per-realm:
#   https://target/.well-known/oauth-authorization-server
#   https://login.target/<tenant>/v2.0/.well-known/openid-configuration
#   https://target/auth/realms/<realm>/.well-known/openid-configuration   (Keycloak)

Read the full file on GitHub · 367 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. 5d ago First seen · 367 lines · 182 tokens per session scan A 4373ba057c46

Subscribe to this mod's changes

attacking-oauth-oidc is a skill published in the GitHub repository trilwu/secskills (137 stars, last pushed 5d ago), licensed MIT. It adds 182 tokens to every session and 4,174 once invoked, about $0.0009 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 2026-09-03.

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