OpenAM: Using arbitrary OIDC requested claims values in id_token and user_info is allowed

Summary

If the "claims_parameter_supported" parameter is activated, it is possible through the "oidc-claims-extension.groovy" script, to inject the value of choice into a claim contained in the id_token or in the user_info. Authorization function requests do not prevent a claims parameter containing a JSON file to be injected. This JSON file allows users to customize claims returned by the "id_token" and "user_info" files. This allows for a very wide range of vulnerabilities depending on how clients use claims. For example, if some clients rely on an email field to identify a user, users can choose to entera any email address, and therefore assume any chosen identity.