REMOVAL - omniauth-kerberos gem may be unmaintained and there are claims it is vulnerable to the "Zanarotti attack"
Our Gemfile specifies:
gem 'omniauth-kerberos', '~> 0.3.0', group: :kerberos
This is the latest release of https://github.com/jgraichen/omniauth-kerberos which has this open issue: https://github.com/jgraichen/omniauth-kerberos/issues/3
I don't currently know enough about kerberos or the claimed attack to know if it is genuine. However, the issue was opened a year ago and remains unaddressed; meanwhile, the last commit to the repository was 5 months ago.
The omniauth documentation suggests an alternative gem: https://github.com/omniauth/omniauth/wiki/list-of-strategies but that was last committed to 5 years ago.