Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 8.6.40 and 9.6.0-alpha.14, the GraphQL WebSocket endpoint for subscriptions does not pass requests through the Express middleware chain that enforces authentication, introspection control, and query complexity limits. An attacker can connect to the WebSocket endpoint and execute GraphQL operations without providing a valid application or API key, access the GraphQL schema via introspection even when public introspection is disabled, and send arbitrarily complex queries that bypass configured complexity limits. This vulnerability is fixed in 8.6.40 and 9.6.0-alpha.14.