Doorkeeper is an OAuth 2 provider for Ruby on Rails / Grape. Prior to version 5.6.6, Doorkeeper automatically processes authorization requests without user consent for public clients that have been previous approved. Public clients are inherently vulnerable to impersonation, their identity cannot be assured. This issue is fixed in version 5.6.6.
Doorkeeper version 4.2.0 and later contains a Incorrect Access Control vulnerability in Token revocation API's authorized method that can result in Access tokens are not revoked for public OAuth apps, leaking access until expiry.
The Doorkeeper gem before 4.2.0 for Ruby might allow remote attackers to conduct replay attacks or revoke arbitrary tokens by leveraging failure to implement the OAuth 2.0 Token Revocation specification.
Cross-site request forgery (CSRF) vulnerability in doorkeeper before 1.4.1 allows remote attackers to hijack the authentication of unspecified victims for requests that read a user OAuth authorization code via unknown vectors.