API Abuse is the misuse or overuse of an API’s legitimate functionality, typically by exploiting the business logic the API was designed to serve rather than a coding vulnerability. This is a critical distinction: in a classic vulnerability exploit, an attacker takes advantage of a flaw in the implementation; in API abuse, the API is used exactly as built – but by the wrong party, for the wrong reason, or at abnormal scale.
Because abuse operates within intended functionality, it often evades traditional security tools that look for malformed requests or known exploit signatures. A well-designed, “perfect” API with no technical flaws can still be abused. Examples include scraping large volumes of publicly available data to assemble valuable datasets, automating account creation, exhausting a promotional offer through automated redemption, enumerating user records through legitimate lookup endpoints, or overwhelming a resource-intensive endpoint. The OWASP API Security Top 10 addresses part of this under “Unrestricted Access to Sensitive Business Flows,” where functionality like buying tickets or posting comments is abused through excessive automation.
API abuse is difficult to catch because each abusive request may look identical to a legitimate one – the problem emerges only in the pattern, volume, or context of the behavior. Abuse specific to a particular business is frequently unaddressed by generic frameworks, since it depends on how that organization’s unique workflows can be exploited.
Defending against API abuse requires understanding normal usage baselines and detecting deviations: rate limiting, behavioral analytics, bot detection, and business-logic-aware monitoring that can distinguish a genuine user from automated exploitation. As APIs increasingly expose raw business functionality – and as automated and agentic clients proliferate – API abuse is widely regarded as one of the most pressing and least-solved categories of API risk, precisely because it exploits legitimate design rather than fixable bugs.