Affected: parse-community parse-server

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.29 and 8.6.49, a user can sign up without providing credentials by sending an empty `authData` object, bypassing the username and password requirement. This allows the creation of authenticated sessions without proper credentials, even when anonymous users are disabled. The fix in 9.6.0-alpha.29 and 8.6.49 ensures that empty or non-actionable `authData` is treated the same as absent `authData` for the purpose of credential validation on new user creation. Username and password are now required when no valid auth provider data is present. As a workaround, use a Cloud Code `beforeSave` trigger on the `_User` class to reject signups where `authData` is empty and no username/password is provided.