CouchDB version 3.0.0 shipped with a new configuration setting that governs access control to the entire database server called
require_valid_user_except_for_up. It was meant as an extension to the long standing setting
require_valid_user, which in turn requires that any and all requests to CouchDB will have to be made with valid credentials, effectively forbidding any anonymous requests. The new
require_valid_user_except_for_up is an off-by-default setting that was meant to allow requiring valid credentials for all endpoints except for the
/_up endpoint. However, the implementation of this made an error that lead to not enforcing credentials on any endpoint, when enabled. CouchDB versions 3.0.1 and 3.1.0 fix this issue.