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.
https://github.com/doorkeeper-gem/doorkeeper/releases/tag/v4.2.0
https://github.com/doorkeeper-gem/doorkeeper/issues/875
http://www.securityfocus.com/bid/92551
http://www.securityfocus.com/archive/1/539268/100/0/threaded
http://seclists.org/fulldisclosure/2016/Aug/105
http://packetstormsecurity.com/files/138430/Doorkeeper-4.1.0-Token-Revocation.html