    def apply_auth(credentials)
      unless auth == credentials
        logouts = auth.keys - credentials.keys

        logouts.each do |database|
          logout database
        end

        credentials.each do |database, (username, password)|
          login(database, username, password) unless auth[database] == [username, password]
        end
      end

      self
    end
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.