ISC2 CISSP Practice Question

Fuzzing, or fuzz testing, is the most effective approach for identifying authentication bypass vulnerabilities in APIs because it systematically sends unexpected, malformed, or random data inputs to the API endpoints to discover how they handle invalid or unexpected inputs. This technique is particularly effective at finding authentication bypass vulnerabilities as it can reveal edge cases where input validation fails or where error handling might expose sensitive information that could assist in bypassing authentication controls.

While schema validation testing is valuable for ensuring API inputs conform to expected formats, it doesn't specifically target authentication logic flaws. Load testing focuses on performance under stress rather than security vulnerabilities. Port scanning is a network reconnaissance technique that identifies open ports and services but doesn't test application-level authentication mechanisms in APIs.