New Tool Catches Hidden Flaws in GraphQL APIs That Standard Security Scanners Miss

GraphQL APIs securing financial services, e-commerce platforms, and social networks frequently harbor critical access-control vulnerabilities that slip past industry-standard security scanners. Researchers have developed GraphQLer, an open-source automated testing framework designed specifically to uncover these hidden flaws in production GraphQL systems.

The Problem with Existing Security Tools#

Standard security testing tools like ZAP and research fuzzers such as EvoMaster evaluate API operations in isolation. This approach leaves dangerous vulnerabilities undetected because many real-world flaws—including Insecure Direct Object Reference (IDOR), Use-After-Free (UAF), and state-dependent injection attacks—require carefully orchestrated sequences of multiple operations to exploit. Since these tools cannot compose multi-step attack chains, they miss the vulnerabilities entirely.

How GraphQLer Works#

GraphQLer builds a typed dependency graph directly from live GraphQL schema introspection data and then synthesizes vulnerability chains: ordered sequences of operations targeting specific flaw classes. The framework employs three complementary detection strategies:

• Topological SCC-traversal: Systematically traverses the API graph to test general reachability
• Cross-user IDOR replay: Probes for broken access control by replaying operations across different user contexts
• CREATE → DELETE → READ synthesis: Constructs sequences designed to expose Use-After-Free vulnerabilities

Real-World Validation#

Testing demonstrated significant practical impact. On a production financial API, GraphQLer identified eight potential vulnerabilities, including denial-of-service vectors that exposed stack traces and implementation details—discoveries made without prior documentation or authentication credentials. Against a self-hosted Saleor instance pinned to the vulnerable CVE-2022-39275 code, GraphQLer reproduced all four broken-access-control mutations documented in the official security advisory.

Across a broader evaluation of 11 public APIs, GraphQLer achieved 85.52% mean PositiveCoverage compared to 29.29% for EvoMaster and 21.80% for ZAP. Across all 21 tested APIs, the tool detected every confirmed IDOR endpoint, exposed UAF behavior on two controlled schemas, and confirmed XSS and SQL injection vulnerabilities on DVGA—while existing baseline tools detected zero chain-based vulnerabilities.