Parse Server versions >= 9.0.0 before 9.10.0-alpha.6 and >= 8.2.2 before 8.6.87 disclose Pointer and Relation target class names through GraphQL validation and input-coercion error messages when public schema introspection is disabled (graphQLPublicIntrospection: false, the default). Because these errors are produced before authentication, authorization, or any resolver runs, an unauthenticated client possessing only the public application ID can trigger errors on Pointer or Relation fields to reconstruct hidden schema class names, partially defeating the schema-hiding protection. Only schema metadata (class names) is exposed; no object data, credentials, or user records are disclosed.