Gartner predicted that by 2025, APIs would be the most frequent attack vector. That prediction proved accurate. High-profile breaches at Twitter, Optus, T-Mobile, and numerous Indian enterprises in the past three years all exploited API security weaknesses — broken object-level authorisation, excessive data exposure, and lack of rate limiting — rather than traditional web application vulnerabilities.
The OWASP API Security Top 10 defines the most critical API vulnerabilities. Broken Object Level Authorisation (BOLA) is the most prevalent: an API endpoint that returns data for a specific object without verifying that the requesting user has authorisation to access that specific object. If changing an ID parameter in an API request returns another user's data, BOLA is present. This is fundamentally a data authorisation failure that automated scanning tools often miss and that requires business logic testing to find.
Authentication and session management failures are the second major category. APIs using long-lived tokens without rotation, tokens transmitted in URL parameters rather than headers, or weak token entropy are common vulnerabilities in APIs built without security review.
API gateways provide the first layer of API security at scale: authentication enforcement, rate limiting to prevent abuse, request validation against API schemas, and TLS termination. Kong, AWS API Gateway, and Apigee are the leading platforms. But gateway security alone is insufficient — it does not address business logic vulnerabilities like BOLA that require application-level testing.
API security testing must be a defined activity in your SDLC. OWASP ZAP, Postman, and dedicated API security testing tools like 42Crunch can automate a significant portion of API security testing when integrated into CI/CD pipelines.
API discovery — maintaining an inventory of all APIs in production including shadow APIs created by development teams outside of official processes — is the prerequisite for API security governance. You cannot secure what you do not know exists.