oauth-oidc-misconfiguration

oauth-oidc-misconfiguration is a skill for Claude Code, Codex from JustineDevs/premortem. It costs 45 tokens per session (555 once invoked), scanned A, a copy of oauth-oidc-misconfiguration, Apache-2.0.

A security testing guide for OAuth 2.0 and OpenID Connect, the common standards behind “Sign in with Google” and similar login systems. It checks whether login callbacks and tokens are correctly tied to the right user and application.

In plain words
What is it for?
Use it to review redirect URLs, state and nonce checks, PKCE, token audience and issuer checks, and callback binding in web, mobile, and single-page applications.
Why use it?
It helps find configuration mistakes that could let attackers redirect login responses, reuse authorization codes, or attach another person's account to a session.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to review redirect URLs, state and nonce checks, PKCE, token audience and issuer checks, and callback binding in web, mobile, and single-page applications.

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

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 oauth-oidc-misconfiguration

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

Your own site · 80×15
<a href="https://agentmods.dev/skills/justinedevs/premortem/oauth-oidc-misconfiguration"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/oauth-oidc-misconfiguration.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 45 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 555 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 100% copy Near-identical to another mod 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 $0.00045 $0.00555
Opus 5 $0.00023 $0.00278
Sonnet 5 $0.00009 $0.00111
Haiku 4.5 $0.00005 $0.00056

Measured 7d ago against content hash 558df7a21e84, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

oauth-oidc-misconfiguration 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 7d 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.

Origin

This is a copy

100% identical to oauth-oidc-misconfiguration — 0 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.

.agents/skills/oauth-oidc-misconfiguration/SKILL.md · 46 lines

What it actually says

SKILL: OAuth and OIDC Misconfiguration — Redirects, PKCE, Scopes, and Token Binding

AI LOAD INSTRUCTION: Use this skill when the target uses OAuth 2.0 or OpenID Connect and you need a focused misconfiguration checklist: redirect URI validation, state and nonce handling, PKCE enforcement, token audience, and account binding mistakes.

1. WHEN TO LOAD THIS SKILL

Load when:

  • The app supports Login with Google, GitHub, Microsoft, Okta, or other IdPs
  • You see authorize, callback, redirect_uri, code, state, nonce, or code_challenge
  • Mobile or SPA clients rely on OAuth or OIDC flows

For token cryptography and JWT header abuse, also load:

2. HIGH-VALUE MISCONFIGURATION CHECKS

Theme What to Check
state handling missing, static, predictable, or not bound to user session
redirect_uri validation prefix match, open redirect chaining, path confusion, localhost leftovers
PKCE missing for public clients, code verifier not enforced, downgraded flow
OIDC nonce missing or not validated on ID token return
token audience and issuer weak aud / iss checks, cross-client token reuse
account binding callback binds attacker identity to victim session
scope handling broader scopes granted than the user or client should receive

3. QUICK TRIAGE

  1. Map the full flow: authorize, callback, token exchange, logout.
  2. Replay callback flows with altered state, nonce, and redirect_uri.
  3. Compare SPA, mobile, and web clients for weaker validation.
  4. Check whether one provider account can be rebound to another local account.
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. 7d ago First seen · 46 lines · 45 tokens per session scan A 558df7a21e84

Subscribe to this mod's changes

oauth-oidc-misconfiguration is a skill published in the GitHub repository JustineDevs/premortem (2 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 45 tokens to every session and 555 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to oauth-oidc-misconfiguration, differing in 0 lines, and is treated as a copy.

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