APIs are your most exposed back door. We test them the way an attacker would.

An endpoint exposes an identifier but fails to verify the user's permission over that object. It is the #1 API vulnerability and the most common cause of data breaches.

JWT with weak algorithms, credential stuffing without rate limits, predictable password recovery, sessions without revocation.

The API allows reading or modifying unauthorized attributes (mass assignment, excessive data exposure).

No rate limiting or quotas: exhaustion of CPU, memory, disk or cloud budget (thousands-of-dollars bills from paid-API calls).

Admin endpoints reachable from user roles. Escalation by simply changing the URL or HTTP verb.

Automatable flows without anti-bot protection: mass fraud, denial-of-inventory, promotion abuse.

The API follows URLs without validation. Allows reaching internal resources (cloud metadata, private networks, localhost).

Permissive CORS, missing headers, unrestricted methods, verbose errors, frameworks with insecure defaults.

Shadow APIs, exposed deprecated endpoints, old unpatched versions. You can't protect what you don't know exists.

Blind trust in third-party API responses: if the third party is compromised, your API becomes the vector.