What Is API Security?

In 2023, the Open Web Application Security Project (OWASP) published an updated list of the Top 10 API Security Risks to help businesses identify, understand, and protect themselves from the most dangerous threats to API security. The list includes:

1. Broken Object-Level Authorization: Attackers can manipulate object identifiers in API calls to access data they shouldn’t see. Organizations can reduce this risk by validating user permissions for every request and enforcing object-level access controls to prevent data exposure across endpoints.
   
   
2. Broken Authentication: Weak or poorly implemented authentication mechanisms can allow attackers to impersonate legitimate users or steal credentials. APIs should rely on strong identity verification protocols such as OAuth, OpenID Connect (OIDC), and multi-factor authentication (MFA) to prevent account takeovers.
   
   
3. Broken Object Property-Level Authorization: APIs that don’t properly validate access permissions for individual object properties can unintentionally leak sensitive data. Applying fine-grained access controls and consistent authorization checks across all API layers helps close these gaps.
   
   
4. Unrestricted Resource Consumption: Without rate limiting or throttling, APIs can be overwhelmed by excessive requests or distributed denial-of-service (DDoS) attacks. Implementing quotas and intelligent traffic management through API gateways helps maintain performance and availability under heavy load.
   
   
5. Broken Function-Level Authorization: Misconfigured permissions or exposed endpoints may allow users to perform unauthorized actions. Restricting sensitive operations to specific roles and enforcing least-privilege principles at the function level significantly reduces this risk.
   
   
6. Unrestricted Access to Sensitive Business Flows: Arising from the automated exploitation of APIs used to carry out business functions, such as making online purchases or posting comments to social media.Behavioral analytics and anomaly detection can identify unusual patterns and stop attackers before damage occurs.
   
   
7. Server-Side Request Forgery (SSRF): These flaws can allow attackers to bypass firewalls and virtual private networks (VPNs) to compromise APIs that fetch remote resources. Sanitizing input parameters, restricting external requests, and segmenting internal networks all help contain SSRF attacks.
   
   
8. Security Misconfiguration: Default credentials, exposed debug endpoints, or missing security headers can leave APIs and their support systems vulnerable to malicious breaches or attacks. Automated configuration management and continuous security assessments help ensure APIs stay hardened against evolving threats.
   
   
9. Improper Inventory Management: Shadow and zombie APIs—with API sprawl where developers create many APIs, there can be forgotten legacy APIs that are publicly available but not monitored. These APIs lack security measures and become an easy target for attackers. Maintaining an up-to-date API inventory and routinely scanning for inactive or deprecated endpoints ensures nothing slips under the radar.
   
   
10. Unsafe Consumption of APIs—Integrating with third-party APIs that lack proper security controls can open indirect attack paths. Organizations should validate input and output data, review third-party security practices, and use API gateways to enforce consistent security standards across all integrations.

As attacks on APIs become more prevalent, businesses of all sizes are at risk. Some of the largest and most secure companies in the world have had their APIs compromised in just the last few years alone, including Honda, Dell, and T-Mobile.

In 2024, vulnerability exploit attacks also compromised the private accounts of hundreds of millions of users of services like LinkedIn, Facebook, Snapchat, Duolingo, and X (formerly Twitter).