In strategy.rb in OmniAuth before 1.3.2, the authenticity_token value is improperly protected because POST (in addition to GET) parameters are stored in the session and become available in the environment of the callback phase.
https://www.debian.org/security/2018/dsa-4109
https://github.com/omniauth/omniauth/pull/867/commits/71866c5264122e196847a3980c43051446a03e9b