OAuthenticator is software that allows OAuth2 identity providers to be plugged in and used with JupyterHub. JupyterHub < 5.0, when used with `GlobusOAuthenticator`, could be configured to allow all users from a particular institution only. This worked fine prior to JupyterHub 5.0, because `allow_all` did not take precedence over `identity_provider`. Since JupyterHub 5.0, `allow_all` does take precedence over `identity_provider`. On a hub with the same config, now all users will be allowed to login, regardless of `identity_provider`. `identity_provider` will basically be ignored. This is a documented change in JupyterHub 5.0, but is likely to catch many users by surprise. OAuthenticator 16.3.1 fixes the issue with JupyterHub 5.0, and does not affect previous versions. As a workaround, do not upgrade to JupyterHub 5.0 when using `GlobusOAuthenticator` in the prior configuration.