Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.78 and 9.9.1-alpha.2, Parse Server's GraphQL endpoint discloses schema metadata to unauthenticated callers through Did you mean ...? suggestions embedded in GraphQL validation-error messages. An unauthenticated caller who knows only the public application id can iteratively send malformed queries to reconstruct class names, field names, argument names, mutation names, and input-object fields. This issue has been patched in versions 8.6.78 and 9.9.1-alpha.2.