APIs power the core capabilities of software applications, such as real-time communication, third-party integrations, personalized user experiences, automated workflows, and cross-platform interoperability. The adoption of application programming interfaces continuously scales. According to surveys by SlashData and MuleSoft, nearly 90% of developers and 84% of businesses are already leveraging APIs as a core part of their software strategies. And, unfortunately, the attack surface they expose grows hand in hand.
With the rapid shift toward cloud-native architectures and distributed systems, API traffic now accounts for more than 90% of all web traffic, and they continue to dominate the data exchange layer of advanced applications. This makes APIs an attractive target for cybercriminals. Major breaches in recent years have stemmed directly from poorly secured APIs. According to a survey by Akamai, 84% of security professionals reported experiencing at least one API security incident in the past year. As an outcome, they’ve exposed millions of user records, highlighting the consequences of weak API security in high-stakes environments.
APIs are primarily designed for software applications to access and use automatically, rather than for direct human interaction. They often lack built-in visibility, making traditional security measures less effective. Developers may focus on rapid feature delivery over secure implementation, leaving exploitable gaps in production.
This article breaks down the top 10 API security challenges, explaining how each risk works in a real environment, why it matters, and what teams can do to mitigate it.
Table of Contents:
Why API Security Is Critical
In 2025, as businesses expand their use of microservices and cloud-native architectures, APIs remain central to digital operations. REST, gRPC, GraphQL, and other types of communication protocols serve as critical connectors across SaaS platforms, IoT ecosystems, and third-party integrations.
Nonetheless, the ubiquity of APIs has a certain risk, as it can expose business logic, user data, and backend systems to the open internet. For instance, the T‑Mobile breach in early 2023 alone exposed data from approximately 37 million customer accounts via an API flaw. Every exposed endpoint becomes a potential target for an attack. Besides, while traditional web applications can often rely on layered security mechanisms, APIs require dedicated protection that addresses their specific setbacks, such as broken object-level authorization, excessive data exposure, and lack of proper rate limiting.
Recognizing the threat of this sector, the OWASP Foundation has introduced the API security top 10 project, where they describe a curated list of the most common and dangerous vulnerabilities found in APIs. These have also been directly linked to real-world breaches across industries.
Most Common API Security Challenges
The prevalent part of API integration challenges is introduced inherently by their architecture, which introduces particular vulnerabilities that are often overlooked during development. Basic web apps that are familiar to all of us hide business logic behind a UI, whereas APIs expose that logic to consumers and, by extension, attackers.
Broken Object-Level Authorization (BOLA)
Broken Object-Level Authorization, or BOLA, remains ranked as the most critical API security issue, topping the API security top 10 by OWASP. This vulnerability occurs when APIs fail to enforce access controls on object-level requests properly. In practice, this implies that an attacker can manipulate object identifiers (such as user IDs or transaction IDs) in API calls to access data they shouldn’t be authorized to view or modify.
Consider a scenario in a banking application where the API request GET /accounts/4321 returns account data. If the API fails to verify whether the authenticated user has permission to access account 4321, an attacker who guesses or enumerates account IDs can seize the opportunity to extract information belonging to other users. We would like to emphasize that it is not a hypothetical consequence but has been exploited in real-world breaches where attackers accessed private customer data simply by manipulating request parameters.
At PLANEKS, we proactively eliminate such vulnerabilities through robust access control enforcement, solid authorization logic, and domain-specific threat modeling, all integral to our professional API integration services.
How to detect and prevent it
To combat and eliminate BOLA vulnerabilities, developers should perform in-depth authorization checks at the object level, in addition to doing so only during authentication. Prevention requires implementing fine-grained access control on every endpoint that interacts with user-owned resources. Authorization logic is another practice to enforce consistently across all CRUD operations, and APIs should never rely solely on client-side controls to protect access to sensitive objects.
Inadequate Authentication & Authorization
Weak or inconsistent authentication mechanisms are among the most common API security risks. Some APIs rely on concise methods, such as static API keys, which can be easily compromised or leaked. Even more critically, software engineers often conflate authentication (verifying who the user is) with authorization (verifying what the user is allowed to do), resulting in misconfigurations that allow unauthorized actions.
Confusion between user auth vs. app auth
Inadequate adoption of modern security protocols contributes to this problem. APIs that don’t use OAuth2 or OpenID Connect may struggle to handle token management, session expiration, and role-based access control securely. Aside from that, failing to differentiate between user-level authentication and application-level access can potentially open the door to privilege escalation.
Recommended best practices
To strengthen API authentication and authorization, you should adopt OAuth2 with scoped access tokens and refresh tokens. OpenID Connect can add an identity layer on top of OAuth 2, allowing for federated login and richer user context. Token expiration, revocation, and proper storage practices are inalienable to maintain integrity throughout the session lifecycle.
Excessive Data Exposure
APIs sometimes return more data than was requested, assuming the client will filter out what they don’t need. This approach directly optimizes development, but at the same time, it creates a massive liability. Overexposing data, such as internal fields, metadata, or personally identifiable information (PII), can provide attackers with the context they seek to launch further exploits, perform social engineering, or escalate privileges.
Need for data filtering and field-level encryption
Mitigating excessive data exposure requires adopting a principle of least privilege for API responses. In these terms, technicians should explicitly define which fields are exposed for each endpoint and role. Field-level encryption should also be adopted where applicable, particularly for sensitive attributes such as credit card data or health information. Therefore, APIs should only deliver back the minimum viable data necessary to serve the client’s request and nothing more.
Lack of Rate Limiting and Throttling
Without adequate rate limiting and throttling, APIs are vulnerable to brute-force attacks, credential stuffing, and denial-of-service (DoS) attempts. An attacker can overwhelm backend systems by bombarding them with a high volume of requests, leading to degraded performance or total outage. Public-facing APIs, specifically those exposed without authentication, are the primary goals for rate limiting and throttling strategies.
API gateway capabilities and threat detection
To prevent API abuse, the development team should implement adaptive rate limiting based on IP address, user identity, and behavioral patterns. API gateways can enforce usage quotas, burst control, and geo-based restrictions. Anomaly scoring and behavioral baselining are threat detection mechanisms that can proactively flag suspicious request patterns and block potential attackers in real time.
Mass Assignment Vulnerabilities
Mass assignment occurs when an API blindly accepts and binds incoming request parameters to internal object models, allowing users to update fields they should not be able to control. This vulnerability is often introduced through auto-mapping frameworks that prioritize convenience over control. For instance, if a PUT /users/123 endpoint accepts JSON and maps it directly to a user object, an attacker could add unexpected fields, such as role: admin or is_verified: true, to escalate privileges.
How to validate and whitelist request fields
Software engineers should meticulously define which fields are accepted in each API endpoint. Blacklisting is insufficient; instead, it’s reasonable to apply whitelisting – a core practice among API security trends – allowing attributes and validating their types, formats, and ranges. Request payloads should be parsed into DTOs (Data Transfer Objects) with strict schema validation, making sure only intended fields are processed.
Logging and Monitoring Failures
One of the highly neglected yet impactful security gaps in API ecosystems is the absence of effective logging and monitoring. When an API breach occurs, delayed detection dramatically increases the damage. Without visibility into API activity, with its access patterns, failed logins, or unusual payloads, teams are left in the dark and obscurity until symptoms become catastrophic.
Role of centralized logging and SIEM tools
To fill this gap, APIs should integrate with centralized logging platforms and SIEM (Security Information and Event Management) tools. Structured logging should capture key metadata, including request origin, user identity, method, endpoint, and status, without leaking confidential information. Real-time can also considerably help in suspicious activity, and audit logs must be protected from tampering to preserve incident integrity.
Security Misconfiguration
Security misconfiguration is a catch-all category that incorporates a broad range of mistakes, like leaving debug modes enabled in production, misconfigured CORS policies, overly permissive headers, and exposed admin interfaces. Such issues often arise during deployment or maintenance rather than coding, which makes them difficult to track without automated checks.
Importance of secure deployment practices
Secure-by-default deployment practices are typically implemented to deal with such issues. Infrastructure-as-Code (IaC) tools should incorporate automated security scans, while continuous delivery pipelines are required to validate configurations before pushing to production. You should hire API developers who ensure that secure tech environments are hardened, secrets are managed through secure vaults, and audit logs are reviewed regularly to identify and eliminate missteps as soon as possible.
Improper Asset Management
Many organizations struggle to keep track of their APIs, even more often if teams scale, systems progress, and older services are deprecated but not decommissioned. Shadow APIs, those that exist outside of official documentation or inventory, can turn into a significant threat. Forgotten endpoints may lack authentication, use outdated libraries, or run on unsupported infrastructure, draining the safety levels of your solution.
Risks
Even well-documented APIs can become liabilities if versioning is ignored or endpoints are left exposed beyond their intended lifespan. Fragmentation in API management tends to create blind spots in monitoring, patching, and incident response.
Mitigation
Effective asset management requires automated discovery of APIs across environments, such as internal, external, and partner-facing endpoints. Here, tools like API gateways and observability platforms can help maintain an up-to-date inventory, track usage patterns, and enforce version control. Every API, regardless of its exposure level, must be well-documented, thoroughly tested, and closely tracked as part of a centralized security strategy. This is even more critical for AI API integration, which often processes sensitive data and relies on dynamic models, making them particularly susceptible to misuse or unintended exposure if not properly governed.
Lack of Transport Layer Protection
Transmitting sensitive data without enforcing HTTPS or adopting outdated TLS configurations makes APIs more sensitive to man-in-the-middle (MITM) attacks. When data travels over insecure channels, it can be intercepted, altered, or replayed, compromising both confidentiality and integrity. Unfortunately, some APIs still allow HTTP fallback or support deprecated protocols like TLS 1.0 or 1.1, which are no longer considered secure.
Risks
Attackers can exploit unsecured transport to hijack authentication tokens, intercept user credentials, or inject malicious payloads. Therefore, mobile apps and IoT devices that interact with APIs over weak connections are particularly vulnerable.
Mitigation
APIs should disable older TLS versions and adopt modern configurations, including strong cipher suites and forward secrecy, to enhance security. HTTP Strict Transport Security (HSTS) headers should be adopted to prevent protocol downgrades and ensure clients connect securely by default, instead of relying on manual HTTPS redirects or allowing insecure HTTP connections.
Business Logic Vulnerabilities
While many API attacks target technical flaws, some of the most damaging breaches stem from broken business logic. Such flaws occur when APIs perform exactly as coded, but the logic itself can be exploited. For instance, an attacker may abuse a refund endpoint by repeatedly invoking a valid transaction or manipulating order workflows to circumvent payment verification.
Risks
Business logic issues are inherently complicated to detect through automated scans because they involve understanding the application’s intended behavior, which often demands manual inspection. Such attacks often appear as legitimate usage but lead to unintended consequences, such as financial loss, data manipulation, or privilege abuse.
Mitigation
As was mentioned, the most efficient practices are manual code reviews, threat modeling, and exploratory testing. Developers should identify abuse cases and implement safeguards against workflow manipulation, such as one-time tokens, operation limits, and consistent state validation. Testing is required to represent real-environment adversarial behavior to uncover edge cases that automated tools can’t detect.
Real-World Examples of API Security Breaches
One of the most severe API-related breaches occurred at T-Mobile, where attackers exploited an unsecured API lacking proper authentication and rate limiting. They’ve successfully gained unauthorized access to sensitive data from over 50 million individuals, covering names, Social Security numbers, and ID details of former, current, and prospective customers. Around 850,000 prepaid users also had their account PINs exposed.
The Peloton breach demonstrates how weak API security can compromise user privacy at scale. A security researcher found that unauthenticated API endpoints returned sensitive data, covering user IDs, workout stats, age, gender, and even private profiles. The APIs suffered from broken authentication, missing authorization, and excessive data exposure, all top OWASP risks. Even after adding login requirements, Peloton failed to restrict what authenticated users could access.
Sadly, in both examples, the problems for API security weren’t due to sophisticated zero-day exploits, but rather to basic oversights like weak access control, misconfigured endpoints, and a lack of secure defaults.
How to Address API Security Challenges
Effectively securing APIs requires a fast yet structured and layered strategy that is embedded across the entire development lifecycle. Organizations must adopt modern security practices that span design, development, deployment, and ongoing monitoring.
If you’re planning an API-related project, using an API development cost calculator can help you estimate expenses more accurately and manage your investment wisely. Vitally important is allocating sufficient resources to implement proven security practices from the start, ensuring your APIs remain robust, compliant, and resilient against evolving threats.
Shift-Left Security in API Development
A fundamental principle is shift-left security, which means integrating security from the earliest stages of API development. This implies conducting threat modeling during the design phase, enforcing secure coding standards during implementation, and integrating automated security testing into CI/CD pipelines. Teams should treat API schemas and specifications as security artifacts, validating them continuously to catch misconfigurations and insecure patterns before they reach production.
Use of API Gateways and WAFs
To control and inspect traffic, many teams rely on API gateways and Web Application Firewalls (WAFs). These tools act as frontline defenses, enabling features such as rate limiting, authentication enforcement, input validation, and anomaly detection. API gateway security also streamlines the enforcement of consistent protection policies across multiple microservices and endpoints. At the same time, WAFs secure against common web threats, such as injection attacks and cross-site scripting.
Secure Coding Practices and Testing
No one canceled secure coding practices – they still remain inalienable. Thus, technicians must sanitize inputs, validate data structures, and avoid automapping request payloads to internal models. Specialized testing methods, such as fuzzing, which injects malformed or unexpected data to uncover bugs, and penetration testing, which simulates real-world attacks, help uncover edge-case vulnerabilities that can be left behind by standard QA. When considering the time to integrate an API, we should essentially factor in that thorough security testing is essential to ensure a resilient and trustworthy integration.
Authentication Best Practices
APIs should adopt OAuth2 for delegated access and use JWTs (JSON Web Tokens) with clearly defined scopes and expiration policies. Consequently, clients only gain access to the particular resources they need for a limited period. To further strengthen integrity and mitigate token leakage, it’s reasonable to implement refresh tokens, token revocation mechanisms, and audience restrictions.
Encrypt Sensitive Data in Transit and at Rest
Sensitive data needs to be encrypted both in transit and at rest. All API traffic should be transmitted over HTTPS with modern TLS configurations, and data stored in databases or logs must be encrypted using strong, rotating keys. Therefore, the impact of interception or unauthorized access is decreased.
Scenarios engaging finance, insurance, and travel API Integration must adopt strong encryption protocols as a foundational security measure. In these sectors, APIs routinely transmit and store highly sensitive data, such as personally identifiable information (PII), payment credentials, policy documents, and travel itineraries, on behalf of both businesses and their customers. They are both frequent attack vectors and are legally obligated to adhere to comprehensive data security regulations, such as PCI DSS, GDPR, and HIPAA.
Regular Audits and Monitoring
Tech teams should carry out regular audits of their API inventories, configurations, and access patterns. Automated monitoring tools can identify unusual activity (such as credential stuffing attempts or rapid access from a single IP), enabling teams to act in real-time. Structured logging, integrated with SIEM platforms, provides compliance reporting alongside post-incident forensic capability.
Implementing Zero Trust Architecture for APIs
Finally, embracing a zero-trust architecture for APIs redirects the mindset from implicit trust (e.g., “it’s on our network, it’s safe”) to continuous verification. Zero-trust architecture is a security framework that assumes no user, device, or system (be it inside or outside the network perimeter) should be trusted by default. Instead, it enforces strict identity verification, access controls, and continuous monitoring for every access request. This approach also perfectly aligns with best B2B API integration practices and has proven to be useful in practice – 39% of financial organizations reported extensive adoption of Zero Trust architecture, resulting in average savings of $850,000. Each API call should be authenticated, authorized, encrypted, and monitored regardless of its origin and creators. Zero trust requires micro-segmentation, strong identity assurance, and contextual access control, ensuring that no user or service is trusted by default.
Tools and Resources for API Security
Addressing API key security risks effectively requires the right set of tools, frameworks, and resources that support both structured design and reactive protection. In case all of these aspects are in place, development and security teams can identify vulnerabilities early, implement consistent policies, and continuously monitor API behavior in production.
API Security Testing Tools
To detect misconfigurations and vulnerabilities during development and testing, software engineers rely on tools like Postman, Burp Suite, OWASP ZAP, and 42Crunch. Postman, while primarily known as an API collaboration and testing platform, now comprises security test automation features. Burp Suite and ZAP are dynamic analysis tools that simulate real-world attacks to determine flaws such as injection, broken authentication, or data leakage. 42Crunch focuses specifically on API contract security and integrates with CI/CD to validate OpenAPI specs against known risks.
API Gateways
For runtime protection, API gateways such as Kong, Apigee, and AWS API Gateway provide centralized enforcement of rate limiting, access control, logging, and request validation. These platforms help standardize security across services and enable dynamic threat mitigation and traffic shaping, which is a pretty sharp need for public-facing or high-traffic APIs.
OWASP API Top 10 Project
The OWASP API security top 10 is the industry-standard reference for understanding and handling API vulnerabilities. Updated regularly, it highlights the most significant issues developers must account for, such as broken object-level authorization, excessive data exposure, and improper asset management. The project also provides remediation advice, sample attack vectors, and tried-and-true methodologies for secure development.
Resources for Secure API Design
For teams looking to apply API security best practices from the ground up, several resources can guide secure architecture decisions.
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- The OWASP Cheat Sheet Series provides practical guidance on implementing authentication, input validation, and transport-layer protection.
- Documentation from major cloud providers like Amazon Web Services, Microsoft Azure, and Google Cloud also includes blueprints and templates for secure API architecture.
- Security-focused courses and certifications, such as those from the Cloud Security Alliance or SANS Institute, can help upskill teams on API-specific threats and defense strategies.
Conclusion
We can’t imagine modern software without APIs, but their openness, if not properly secured, leaves them highly vulnerable. As we may conclude, even small oversights in authentication, data handling, or configuration can lead to severe breaches and lasting reputational damage.
Embed secure coding, proactive monitoring, and continuous validation in your delivery pipeline to fight against common API security issues. When it comes to your tech team, secure API development should be perceived as a shared responsibility across development, DevOps, and architecture. Educating your team on API-specific risks and design patterns is another effective way to ensure long-term resilience.
At PLANEKS, we build and integrate APIs with security in mind from the outset, tailoring solutions to your business logic, industry nuances, and technical constraints. Are you scaling a product or connecting third-party services? Our team is here to ensure that your APIs are robust, hardened, and resilient. Let’s discuss how to fortify your API infrastructure before threats become incidents.
