NL Portal Backend Libraries provide backend components for Dutch government portals that interact with residents, customers, suppliers, and partner organizations. In versions up to and including 3.0.0, deployments using the shipped default configuration exposed two GraphQL developer features without requiring authentication: the GraphiQL playground, an interactive UI for issuing GraphQL queries; and schema introspection, which lets a caller download the full description of every query, mutation, type, and argument the API supports. Anyone who could reach the /graphiql endpoint could open the playground in a browser, pull the full schema, and use that to map out the API and craft calls against it. By itself this does not leak user data, but it removes the guesswork from attacking the rest…