OAuthenticator is an OAuth token library for the JupyerHub login handler. CILogonOAuthenticator is provided by the OAuthenticator package, and lets users log in to a JupyterHub via CILogon. This is primarily used to restrict a JupyterHub only to users of a given institute. The allowed_idps configuration trait of CILogonOAuthenticator is documented to be a list of domains that indicate the institutions whose users are authorized to access this JupyterHub. This authorization is validated by ensuring that the *email* field provided to us by CILogon has a *domain* that matches one of the domains listed in `allowed_idps`.If `allowed_idps` contains `berkeley.edu`, you might expect only users with valid current credentials provided by University of California, Berkeley to be able to access the JupyterHub. However, CILogonOAuthenticator does *not* verify which provider is used by the user to login, only the email address provided. So a user can login with a GitHub account that has email set to `<something>@berkeley.edu`, and that will be treated exactly the same as someone logging in using the UC Berkeley official Identity Provider. The patch fixing this issue makes a *breaking change* in how `allowed_idps` is interpreted. It's no longer a list of domains, but configuration representing the `EntityID` of the IdPs that are allowed, picked from the [list maintained by CILogon](https://cilogon.org/idplist/). Users are advised to upgrade.