API Security: Beyond OWASP Top 10

Nobody can deny the speed and efficiency that comes with the advent of APIs. APIs have revolutionized how software systems communicate, enabling integrations and functionalities that were once difficult to achieve. We often hear boardroom conversations echoing the sentiment: “If it’s not supported natively, let’s use APIs to achieve it.” Today, APIs are everywhere—used for monitoring, configuration management, incident response, and virtually anything that requires automation or data exchange. Organizations are leveraging APIs extensively, and with their widespread use, vulnerabilities naturally follow. It’s no surprise that OWASP has dedicated an entire Top 10 category to API Security. However, while OWASP Top 10 is a critical starting point, focusing only on it might leave some significant security gaps unaddressed. This article will explore what OWASP Top 10 doesn’t fully cover in API security.

Unknown Exposed APIs

One of the most insidious risks organizations face is the presence of unknown or shadow APIs—APIs exposed to the public without the organization's awareness. These APIs often operate over standard HTTP/S protocols, making them easy to miss but easy targets for attackers. Legacy APIs, forgotten endpoints, or those inadvertently exposed during development are particularly dangerous. Organizations often struggle to maintain an updated inventory of their exposed APIs.

To combat this, leveraging External Attack Surface Management (EASM) tools has become essential. These tools must be intelligent enough to differentiate between standard HTTP web traffic and API-specific endpoints. Additionally, they should integrate with continuous alerting mechanisms to notify security teams when new APIs are exposed. Beyond detection, these tools should allow administrators to quickly assess and either accept or shut down newly discovered APIs, ensuring no unapproved endpoints remain accessible.

Robust CI/CD Framework

In the fast-paced world of software development, continuous integration and continuous deployment (CI/CD) pipelines have become a norm. However, the rapid development pace can introduce vulnerabilities if not properly managed. API security testing should be an integral part of the CI/CD process, not an afterthought. Relying solely on runtime security controls is not enough—vulnerabilities need to be addressed before the code reaches production.

Organizations need to implement API-focused code scanning tools that can automatically scan and validate API code during the build and development phases. These tools should be capable of identifying security flaws specific to API logic, such as improper authentication, broken object-level authorization, and data leakage. Integrating these scanners with runtime security controls, such as Web Application Firewalls (WAF) and Dynamic Application Security Testing (DAST) tools, can ensure that a DevSecOps approach extends to API security. This holistic security framework will help secure the API lifecycle from development to deployment and beyond.

Rethinking Bot Identification

APIs were inherently designed for machine-to-machine (M2M) or business-to-business (B2B) communication, where servers, devices, or applications interact without human intervention. Traditional bot identification techniques, such as CAPTCHA challenges or behavioral analytics, may fall short in such scenarios. These methods are designed to distinguish between human and non-human behavior, but they may inadvertently block legitimate API communication between machines, which can be problematic in automated environments.

Bot identification for APIs requires a more nuanced approach. Instead of traditional CAPTCHAs, security teams need to explore mechanisms like token-based authentication, mutual TLS (mTLS), or API key management that ensures only authorized machines can access the API. Additionally, implementing rate limiting, anomaly detection, and behavioral monitoring can help mitigate the risk of bots abusing your APIs without interrupting legitimate traffic. Advanced AI-driven bot management solutions can also learn and adapt to differentiate between good bots (e.g., search engine crawlers) and malicious bots.

Addressing API-Specific Threats Beyond OWASP

While the OWASP API Security Top 10 is a great foundation, it doesn’t encompass all the potential security threats that modern APIs face. Here are a few additional areas that organizations should pay attention to:

• GraphQL-Specific Risks: APIs using GraphQL are particularly susceptible to denial-of-service attacks due to the nature of complex queries. Limiting query depth and complexity, as well as disabling introspection in production environments, can mitigate some of these risks.
• Machine Learning (ML) API Security: APIs exposing machine learning models can be vulnerable to model inversion attacks or adversarial inputs, where attackers manipulate the model’s behavior to gain unauthorized insights or control. Protecting these APIs requires not just traditional API security practices but also specialized measures to defend against ML-specific threats.
• Replay Attacks: APIs handling sensitive operations like financial transactions can be vulnerable to replay attacks if proper measures, such as nonces and timestamp validation, are not in place. Ensuring that each API request is unique and cannot be replayed is critical to securing sensitive workflows.
• Supply Chain Vulnerabilities: APIs are often built on or integrated with third-party libraries, making them vulnerable to supply chain attacks. Regularly auditing dependencies, monitoring for vulnerabilities, and enforcing strict version control can help minimize the risk from compromised components.

The Need for a Complete Framework

In conclusion, focusing solely on the OWASP API Security Top 10 isn’t enough to protect your APIs. Organizations need a comprehensive API security framework that addresses a broader range of risks. This framework should include tools for discovering unknown APIs, robust CI/CD integration for secure API development, advanced bot detection techniques for API traffic, and specialized protections for emerging threats like GraphQL and machine learning APIs.

By looking beyond OWASP Top 10 and adopting a more holistic security posture, organizations can better safeguard their APIs and the valuable data they handle.

Are you exposing APIs? Comment below if you see any other challenges not covered above.