GraphQL security
GraphQL security protects resolver authorization, input handling, and the computational cost of flexible queries.
What it means
GraphQL security protects resolver authorization, input handling, and the computational cost of flexible queries. A single endpoint may expose many operations and nested resources. Rate limits based only on HTTP requests can miss expensive or batched work inside each query.
A practical example
A dashboard API checks access at relevant resolvers, not just at the top-level query. It limits query depth or cost under its design and reviews whether one request can retrieve unauthorized nested records or trigger excessive computation.
What to check
Inventory exposed fields, enforce resource-specific policy, validate inputs, and bound costly queries. Test batching, aliases, pagination, and nested relationships with users of different permissions.
A common pitfall
Disabling introspection is not a substitute for authorization. Hidden schema details do not prevent a caller who discovers a field from querying it.
Think it through
Why review nested resolvers after securing the top-level query?
Answer: Each nested resource can have separate ownership or permission requirements that the outer operation did not establish.
One endpoint can expose many operations
A fictional learning platform uses GraphQL to retrieve courses, lessons, and progress. A request may traverse several related objects in one operation. Checking authorization only when the top-level course resolver runs can leave a nested lesson or progress resolver exposed through another path. Review permissions where protected data is actually resolved.
Query shape also influences cost. A request with deeply nested relationships or many aliases can cause substantial work even if its text is short. Set limits that reflect the schema and resolver behavior, and observe actual database and downstream calls. A simple request-per-minute limit may not distinguish an inexpensive profile lookup from a costly graph traversal.
Schema visibility is not the main access-control boundary. Restricting introspection may fit a deployment's policy, but a caller can still submit operations they already know. Resolver authorization, input handling, and resource limits must remain effective without relying on the schema being secret.
Trace a nested data request
Draw a fictional request for a course and its enrolled learners. Identify which fields are public, which belong to the current learner, and which require an instructor role. Add an alternate path that reaches a learner through a lesson discussion. Explain whether the same policy follows the protected object on both paths.
Use designated training data to test permitted and denied operations. Include mutation behavior, pagination, and error responses, because a field omitted from the main interface may still be reachable through the API. A clear security review describes the schema relationships, the authority required at each resolver, and the processing budget for complex operations. This is more useful than declaring the single endpoint secure after testing one query.
Related concepts
References & further reading
Original explanations, with primary references for deeper study.
OWASP: GraphQL