API Security Risks and Challenges

APIs are the connectors that allow different applications to communicate and exchange data with other applications, services, and platforms. They enable organizations to easily integrate with external platforms and third-party services and build comprehensive solutions by connecting various components. APIs play an increasingly vital role in modern digital infrastructures because they serve as the connective fabric that links applications and data across distributed environments.

As an example, a travel services web application may offer airline and hotel bookings, car rentals, and destination temperatures and weather forecasts. However, all this flight, weather, and rental data is not stored in the travel application itself. Rather, the web app requests the always-changing, real-time information via APIs published by airlines, car rental agencies, and weather providers. The travel app displays that data for the user to interact with, without storing or managing that data internally, allowing the travel app to seamlessly offer a much more robust set of options to its users.

This blog post explores why APIs have become both popular and essential to modern web application development, while discussing the challenges and security risks that APIs bring with them and the most common API vulnerabilities. It also offers advice on the most effective strategies for securing your APIs.

To understand why APIs are so important to modern app development, it helps to compare how applications were traditionally built versus how they are engineered today. Traditional web applications were often monolithic, consisting of thousands of lines of tightly coupled “spaghetti code.” Any update or change to the application requires modifying large sections of the code, making development slow, complex, and more error-prone.

In contrast, modern web applications are typically made up of independent, modular components—or microservices—that communicate via APIs with each other and/or with an application front end, either web or mobile. Each component can be developed, deployed, and scaled separately, and developers can reuse existing services from internal teams or third-party providers rather than building everything from scratch. APIs simplify and speed up development cycles in the creation of applications, enabling faster iteration based on user feedback, integration of third-party services, and more scalable applications that are easy to manage.

APIs are so foundational to modern app development that organizations are increasingly taking an API-first approach, where the design of applications starts with the API. This has led to a proliferation of APIs: The average organization now manages over 400 APIs within their digital infrastructure, while 68% of organizations use APIs to manage app delivery and security.

However, the ubiquity of APIs brings security risks by expanding an organization’s attack surface, making them a prime target for hackers. They expose critical business logic and often sensitive information (sometimes intentionally, but often unintentionally), such as user credentials, personally identifiable information (PII), financial data, authentication credentials, and business operations like payment processing.

In addition, APIs are often not well managed. While API security is a critical component of any organization’s application security strategy, many organizations’ security teams lack full visibility and control over their growing API estates. This can lead to poor API inventory management and unknown, “shadow” APIs or old, deprecated APIs that are deployed but not documented or managed, creating easy entry points for attackers. According to the F5 2025 State of Application Strategy Report, 58% of organizations call API sprawl a significant pain point.

Moreover, many organizations rely on inadequate tools to secure their APIs. While API gateways and web application firewalls (WAFs) are essential for managing and safeguarding API traffic, they are not sufficient on their own to address the full range of API security risks—particularly in today’s complex, distributed environments.

API security risks extend beyond technical threats to digital infrastructure: they carry significant business implications as well. API attacks can result in financial losses from breach containment costs, legal actions, regulatory fines, or more direct losses from overuse of paid services, fraud, or theft. Operational disruptions are also a risk, as attacks can degrade or disable entire applications or target critical services, negatively affecting the user experience and causing emergency fire drills for security and operations teams. The exposure of sensitive user data or repeated performance issues caused by API abuse can erode customer trust and inflict lasting reputational harm.

Following are the seven most common API security vulnerabilities:

1. Authentication and authorization. Four of the 10 OWASP API security risks include authentication and authorization vulnerabilities, including broken object-level authorization, broken authentication, broken object property-level authorization, and broken function-level authorization.

The risk posed by these threats comes from attackers impersonating legitimate users to manipulate object references or to maliciously execute functions to change or gain access to sensitive information. To protect against these vulnerabilities, implement strong authentication and authorization mechanisms such as OAuth or JSON web token (JWT) with proper access controls.

2. Unrestricted access to business flows. 

The risk of these attacks comes from attackers taking advantage of legitimate business flows in malicious ways. Protecting against these attacks can be challenging because the attacks may appear legitimate and aren’t caused by misconfigurations. To detect these attacks, deploy behavioral analytics to identify automated usage patterns—such as accessing multiple functions faster than a human user could—or implement runtime protection that understands and tracks business logic flows.

3. Injection attacks. These vulnerabilities result when attackers send malicious data or commands as part of an API request, with the goal of manipulating how the backend system processes that input. Common injection attacks include SQL injection, cross-site scripting, or server-side request forgery (SSRF).

Injection attacks pose a significant risk because they can manipulate APIs into passing malicious input to backend services—such as databases, search engines, or operating system commands—which may interpret the input as legitimate instructions. This can result in data breaches, unauthorized access, or unintended execution of functions. To mitigate this risk, it is important to implement robust input validation and sanitization practices, ensuring that APIs only process safe, expected, and properly formatted data.

4. Unrestricted resource consumption. This occurs when a series of API requests overloads resources such as network bandwidth, CPU, memory, or storage. These attacks, also called resource exhaustion, can result in denial of service (DoS), which degrades the performance or availability of the API or the underlying system, leading to downtime.

These types of attacks can severely impact operations by taking down critical services, or an entire application and may generate excessive infrastructure and operational costs—especially when API services can be billed on a per-request basis. To mitigate these risks, implement rate limiting to control the volume of API requests over defined time intervals, enforce maximum size limits on request parameters and file uploads, and establish spending caps for pay-per-use API services.

5. Security misconfiguration. Attackers attempt to find unpatched flaws, services running with insecure default configurations, or unprotected files and directories to gain unauthorized access to APIs. These attacks can occur when security controls such as Transport Layer Security (TLS) or cross-origin resource sharing (CORS) policies have been implemented incorrectly—or not at all—or unnecessary features have been enabled.

The risk here lies in attackers using automated tools to identify and exploit common misconfigurations, potentially gaining access to services and sensitive data. This risk is amplified as modern architectures have become increasingly decentralized and distributed across multicloud environments. To defend against these threats, organizations should embed security throughout the API development lifecycle and enforce strong security policies, including TLS encryption. They should also utilize automated security testing tools and perform regular API security audits to proactively identify and remediate vulnerabilities.

6. Improper inventory management. This occurs when an organization lacks full visibility into their API assets or doesn’t keep them updated. APIs are subject to changes and updates over time, but outdated or insecure API versions may remain in production. In addition, older endpoints may be left running unpatched or with weak security requirements, increasing the risk of attacks and exploits.

Lack of proper API inventory management is risky because hackers can exploit older versions of APIs that haven’t been patched or shadow APIs that haven’t been properly secured. Protecting against these risks requires maintaining an up-to-date inventory of all API endpoints, regularly reviewing and decommissioning unused APIs, and ensuring all APIs are patched and updated regularly with the proper oversight and security controls in place.

7. Unsafe consumption of APIs. Developers often implicitly trust the data obtained from third-party APIs, especially those provided by well-established organizations. As a result, developers may apply less stringent security measures, such as input validation, data sanitization, or transport layer protection, under the assumption that the data from these APIs is inherently safe. This can introduce significant security vulnerabilities if the external API is compromised or behaves unexpectedly.

Trusting the security of integrated third-party APIs introduces significant risk. Attackers may identify these dependencies and exploit weak API protections to send malicious requests, potentially resulting in unauthorized URL redirects, eavesdropping, data interception, or access to sensitive information. To mitigate these threats, always communicate with third-party services over encrypted channels, rigorously validate and sanitize all incoming and outgoing data, avoid blindly following URL redirects, and enforce strict limits on the scope and frequency of interactions with external services.