OWASP API Top 10: How to Secure Your APIs, Complete Guide

Key Takeaways

The OWASP API Security Top 10 highlights the most critical API risks, like broken authorization and misconfigurations, to help teams apply consistent defenses and reduce attack surfaces early in development.
API vulnerabilities such as BOLA, broken authentication, and function-level access flaws can be mitigated through fine-grained authorization, strong authentication protocols, and role-based access controls.
Pynt automates detection of OWASP Top 10 risks during development by integrating into CI/CD pipelines, enabling faster fixes and reducing reliance on manual security reviews.
Pynt’s real-world attack simulation exposes vulnerabilities beyond the OWASP list, helping teams catch gaps between theoretical risks and active threats before production.
Combining OWASP’s framework with Pynt’s automated, shift-left approach improves workflow efficiency, reduces false positives, and strengthens overall API security posture.

What is the OWASP API Security Top 10?

The OWASP API Security Top 10 is a list of the most critical API security risks, maintained by the OWASP Foundation under the OWASP API Security Project. First published in 2019 and updated in 2023, it highlights common weaknesses, including authorization flaws, misconfigurations, and unsafe API consumption. The goal is to help developers and security teams prioritize defenses and apply consistent security controls across their API ecosystems.

Why API Security Matters Today

APIs are now the foundation of modern applications, connecting users, services, and data. Their growing exposure makes them prime targets for brute force attacks, data theft, and abuse of administrative functions. A single poorly secured endpoint can allow attackers to gain access to sensitive systems. By aligning with the OWASP API Security Top 10, organizations can address these risks early, reduce the attack surface, and strengthen resilience against evolving threats.

OWASP API Top 10 Security Risks 2023

The OWASP Foundation publishes the OWASP API Security Project, highlighting the top risks developers and security teams must address. Below are the 10 security risks from the 2023 update, each accompanied by context and practical mitigation strategies.

API1:2023: Broken Object Level Authorization

APIs often expose object identifiers, and without proper access checks, attackers can manipulate them. This creates opportunities to access or modify data that belongs to other users.

How to Mitigate Broken Object Level Authorization (BOLA)

Enforce object-level authorization checks on every endpoint.
Validate user permissions before read, update, or delete actions.
Apply least-privilege roles and scopes.
Audit object access patterns for anomalies.

API2:2023: Broken Authentication

Authentication flaws are a leading cause of account compromise. APIs that fail to enforce strong authentication let attackers impersonate legitimate users and steal sensitive data.

How to Mitigate Broken Authentication

Use secure standards such as OAuth 2.0 or OpenID Connect.
Enforce multi-factor authentication for all accounts.
Protect session tokens with secure storage and expiry rules.
Monitor failed login attempts to prevent brute force attacks.

API3:2023: Broken Object Property Level Authorization

Even if object-level checks exist, APIs may still expose sensitive properties of those objects. This risk allows attackers to escalate privileges or exfiltrate hidden data fields.

How to Mitigate Broken Object Property Level Authorization

Apply fine-grained, property-level access control.
Hide or restrict sensitive fields from unauthorized users.
Enforce role-based serialization rules.
Test APIs for overexposed data fields.

API4:2023: Unrestricted Resource Consumption

Attackers can overwhelm APIs by sending massive requests or large payloads. This drains CPU, memory, or bandwidth, reducing availability for legitimate users.

How to Mitigate Unrestricted Resource Consumption

Implement rate limiting and request throttling.
Validate and restrict payload sizes.
Monitor traffic patterns for anomalies.
Apply quotas per user or client.

API5:2023: Broken Function Level Authorization

When APIs fail to enforce permissions on functions, users may access administrative and regular functions they shouldn’t. This creates a high-risk path to privilege escalation.

How to Mitigate Broken Function-Level Authorization

Verify user roles before allowing function execution.
Separate administrative functions from standard user actions.
Apply least-privilege principles to all roles.
Test role-based access control frequently.

API6:2023: Unrestricted Access to Sensitive Business Flows

Business processes like checkout or payments can be abused when APIs don’t enforce restrictions on workflows. Attackers may commit fraud or disrupt operations.

How to Mitigate Unrestricted Access to Sensitive Business Flows

Enforce strict access controls on sensitive workflows.
Validate business logic step by step.
Monitor usage patterns to detect fraud or abuse
Penetration test business flows regularly.

API7:2023: Server Side Request Forgery (SSRF)

SSRF occurs when APIs process attacker-supplied URLs and make unintended requests. This exposes internal services or external resources to unauthorized access.

How to Mitigate Server-Side Request Forgery

Validate and sanitize all user-supplied URLs.
Restrict outgoing requests to trusted domains.
Use network segmentation and firewall rules.
Disable unused URL parsing features.

API8:2023: Security Misconfiguration

Insecure defaults, verbose errors, or exposed admin panels leave APIs wide open. These security control gaps often result from poor configuration practices.

How to Mitigate Security Misconfiguration

Harden default settings and disable unnecessary services.
Restrict access to management endpoints.
Review and patch configurations regularly.
Use automated tools to detect misconfigurations.

API9:2023: Improper Inventory Management

Organizations that lack full visibility into their APIs expose shadow or outdated endpoints. This improper asset management increases risk.

How to Mitigate Improper Inventory Management

Continuously discover and document all APIs.
Retire or secure deprecated versions.
Integrate APIs into enterprise asset management.
Automate monitoring for new or untracked endpoints.

API10:2023: Unsafe Consumption of APIs

Relying on insecure third-party APIs without validation transfers risks into your own application. A compromised external service can cause data breaches or downtime.

How to Mitigate Unsafe Consumption of APIs

Vet external APIs before integration.
Validate all incoming and outgoing data.
Require authentication for external API calls.
Audit dependencies to identify risky providers.

OWASP API Top 10 Summary Table

OWASP API Top 10 Risks	Description	Mitigation Strategy
Broken Object Level Authorization	Attackers manipulate object IDs to access other users’ data.	Enforce object checks, validate permissions, least privilege, and audit logs.
Broken Authentication	Weak or missing identity validation leads to impersonation.	OAuth/OIDC, MFA, secure token handling, and monitoring brute force attempts.
Broken Object Property Level Authorization	APIs expose sensitive fields without permission checks.	Property-level access control, hide sensitive fields, and enforce role-based serialization.
Unrestricted Resource Consumption	Excessive requests drain resources and cause outages.	Rate limiting, throttle requests, restrict payload size, quotas.
Broken Function Level Authorization	Users execute administrative functions they shouldn’t.	Verify roles, separate admin and user functions, least privilege, and RBAC tests.
Unrestricted Access to Sensitive Business Flows	Critical workflows like payments can be abused.	Workflow access controls, step validation, monitoring, and penetration testing.
Server Side Request Forgery	APIs make requests to attacker-chosen domains.	Validate URLs, restrict domains, segmentation, and disable unsafe parsers.
Security Misconfiguration	Insecure defaults and exposed endpoints create easy targets.	Harden configs, restrict endpoints, patch regularly, automate testing.
Improper Inventory Management	Shadow or outdated APIs remain unprotected.	API discovery, retire old versions, asset management, and automated monitoring.
Unsafe Consumption of APIs	Weak external APIs transfer risks into your system.	Vet APIs, validate inputs, enforce auth, and audit dependencies.

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Did You Know?

OWASP’s API Top 10 omits Injection, yet it ranked as the second most critical issue across 100K+ endpoints tested by Pynt in 2023.

Key Changes from Previous Versions of the OWASP API Top 10

The OWASP Foundation first released the API Security Top 10 in 2019, then updated it in 2023 to reflect how API threats have evolved. The latest version introduces new categories, consolidates others, and shifts focus toward authorization and business logic risks. Notable changes include:

New Risks Added: Unrestricted Access to Sensitive Business Flows, Unrestricted Resource Consumption, Server Side Request Forgery (SSRF), and Unsafe Consumption of APIs were not present in 2019.
Renamed Categories: Improper Assets Management became Improper Inventory Management to emphasize visibility and monitoring.
Merged Risks: Excessive Data Exposure and Mass Assignment are now consolidated under Broken Object Property Level Authorization.
Removed Categories: Injection and Insufficient Logging & Monitoring were dropped, as these risks are addressed in other OWASP projects.
Shift in Emphasis: Stronger focus on authorization flaws (object, property, and function) across multiple layers.
Business Logic Prioritization: Sensitive workflows like payments and order processing are explicitly recognized as top risks.
Modernization of Examples: Updated scenarios include API supply chain threats and insecure third-party consumption.

OWASP API Top 10' updates: new risks, category changes, merged/removed items, auth focus, business logic spotlight.

Other OWASP Top 10 Projects

In addition to APIs, the OWASP Foundation publishes Top 10 lists for web, mobile, and cloud-native applications. Each addresses unique risks while following the same goal: helping teams prioritize the most common and severe security issues.

OWASP Top 10 Project	Focus Area	Key Risks Covered
Web Application Security Top 10	Traditional web applications	Injection flaws, broken authentication, sensitive data exposure, security misconfiguration, cross-site scripting
Mobile Top 10	Mobile apps on iOS and Android	Improper platform usage, insecure data storage, insufficient cryptography, insecure communication
Cloud-Native Application Security Top 10	Cloud-native apps using containers, microservices, and orchestration	Misconfiguration, insecure APIs, inadequate monitoring, weak identity, and access controls

How to Use the OWASP API Top 10 in Your Organization

The OWASP API Top 10 is more than an awareness list. In reality, it is a practical framework teams can use to guide security programs. By aligning policies, testing, and monitoring to these risks, organizations can systematically reduce exposure and strengthen their security controls. Practical ways to apply the OWASP API Top 10 include:

Security Training: Educate developers and architects on the risks and their mitigations.
Threat Modeling: Use the list to identify potential attack paths during design reviews.
Testing Strategies: Incorporate the Top 10 into penetration tests, code reviews, and automated scans.
Prioritization: Focus remediation efforts on risks mapped to the Top 10 to tackle the most impactful weaknesses first.
Governance and Compliance: Map organizational policies and audits to the OWASP API Security Project to show adherence to industry-recognized standards.

Tzvika Shneider

CEO, Pynt

Tzvika Shneider is a 20-year software Security industry leader with a robust background in product and software management.

Expert Tip: Strengthen API Security with Granular Access, Training, Automation, Validation, and Continuous Monitoring

Implement granular access control: Ensure each API endpoint has specific and appropriate access controls to prevent unauthorized access.
Perform regular security training: Keep developers and administrators updated on the latest security practices and threats.
Automate API inventory management: Use tools to dynamically discover and catalog all active APIs to prevent shadow APIs.
Implement strict input validation: Sanitize and validate all incoming data to prevent injection attacks and other vulnerabilities.
Utilize continuous monitoring and logging: Implement real-time monitoring and logging to quickly detect and respond to potential threats.

Pynt vs OWASP Top 10 API Security Vulnerabilities

The OWASP API Security Project highlights the most significant API risks based on industry surveys and expert consensus. It provides a global standard for awareness and prioritization. Pynt, however, takes a different approach. Drawing on thousands of real-world API tests and its unique attack methodology, the Pynt Top 10™ API Security Vulnerabilities Report uncovers where attackers are actually finding weaknesses. Key differences include:

Data Source: OWASP relies on community input and reported incidents, while Pynt’s list comes directly from large-scale testing of live API endpoints.
Risk Alignment: OWASP focuses on broad categories, while Pynt highlights misalignments by showing that some vulnerabilities are exploited more often in practice than the OWASP list reflects.
Impact for Organizations: OWASP helps teams prioritize common risks, but Pynt highlights gaps that could directly affect a company’s security posture if overlooked.
Practical Application: Together, OWASP sets the baseline and Pynt provides the reality check, ensuring teams cover both theoretical risks and those actively exploited in the wild.

For a detailed breakdown of these differences, see the full report: Pynt vs OWASP: Pynt Top 10™ API Security Vulnerabilities.

Pynt vs OWASP comparison on API risk: source, practical focus, risk gaps, fix-ready output, and dual coverage.

How to Mitigate OWASP API Top 10 Security Risks: Quick Cheat Sheet

To mitigate OWASP API Top 10 risks, organizations are encouraged to implement the following security measures:

Use HTTPS: Secure your REST services by only offering HTTPS endpoints to protect data and credentials in transit, ensure data integrity, and authenticate the service.
Implement Access Controls: Apply access control on each API endpoint to manage access based on user authentication, authorization logic, and session management. Centralize user authentication through an Identity Provider (IdP), which issues access tokens.
Use JWTs: Adopt JSON Web Tokens (JWT) for security tokens, ensuring they are protected with a signature or MAC. JWTs carry a set of claims for access control decisions, and their integrity must be validated.
Use API Keys: To mitigate the risk of excessive use or attack on public REST services without access control, use API keys as part of the request, ensuring they are managed securely.
Restrict the Use of HTTP Methods: Limit allowed HTTP methods (e.g., GET, POST, PUT) and reject requests not adhering to these methods to protect against unauthorized actions.
Validate Inputs: Ensure input validation for all incoming data to protect against malicious input, using type constraints, regexps, and validation libraries.
Protect Management Endpoints: Keep management endpoints inaccessible via the Internet or ensure they are secured, especially when accessible, to prevent unauthorized access.
Include Security Headers in HTTP Responses: Implement security-related HTTP headers to instruct browsers on handling responses, such as directives against caching, framing, and content type security.
Apply the Cross-Origin Resource Sharing (CORS) Standard: Use CORS headers to control which cross-domain requests are allowed, ensuring your REST API specifies permitted origins.
Avoid Sensitive Data in HTTP Requests: Do not include sensitive information, like passwords or API keys, in the URL to prevent exposure in web server logs.

Explore more in our OWASP Top 10 Cheat Sheet

Proactive API Security: Shifting Left to Prevent OWASP Top 10 Risks with Pynt

Catching API risks late in the cycle leads to costly fixes and exposed applications. By shifting left and automating security checks, Pynt uncovers vulnerabilities from both the OWASP API Top 10 and the Pynt Top 10™ during development. This approach improves security posture, reduces remediation costs, and accelerates release cycles.

Here’s how Pynt helps uncover OWASP Top 10 API risks and streamline security workflows:

Automated Vulnerability Detection: Continuously scans APIs against OWASP Top 10 risks such as broken authentication, authorization flaws, and security misconfiguration.
Real-World Attack Simulation: Uses Pynt’s unique testing methodology to replicate how attackers exploit APIs in practice, bridging the gap between OWASP theory and real-world threats.
Shift-Left Integration: Embeds directly into CI/CD pipelines so issues are caught during development, not in production.
Faster Remediation: Provides actionable insights that map directly to OWASP categories, enabling developers to fix issues without relying solely on security teams.
Comprehensive Coverage: Identifies both documented risks (OWASP API Security Project) and misalignments uncovered through Pynt research.
Workflow Efficiency: Reduces manual testing effort by automating repetitive checks, freeing security experts to focus on complex problems.
Enhanced Compliance: Helps demonstrate alignment with OWASP Foundation best practices and internal governance requirements.
Improved Collaboration: Offers developer-friendly reports and guidance, closing the gap between engineering and security teams.

Source: Pynt VS OWASP: Pynt Top 10™ API Security Vulnerabilities Report, 2024

Conclusion

APIs drive critical business operations and customer experiences, but they also open new opportunities for attackers. The OWASP API Top 10 helps teams focus on the most common risks, while the Pynt Top 10™ highlights how those risks play out in real environments. Using both together gives security and development teams a balanced view of theory and practice. When automated testing and shift-left strategies are in place, vulnerabilities can be discovered and fixed before release. The result is stronger applications, lower remediation costs, and greater confidence in the security of every API.

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FAQs

What is the OWASP Top 10 used for?

‍The OWASP Top 10 is an awareness document that highlights the most critical security risks in a given area, such as APIs, web, or mobile. It helps organizations prioritize defenses, train developers, and align with industry-recognized best practices.

How is OWASP Top 10 calculated?

‍OWASP compiles the Top 10 using community surveys, expert input, and real-world incident data. The final list reflects the risks that are most prevalent and impactful across industries.

What is the difference between OWASP and CWE?

‍OWASP provides awareness lists and practical security guidance, such as the OWASP API Top 10. CWE (Common Weakness Enumeration) is a comprehensive catalog of specific software weaknesses used for classification and research.

Who maintains OWASP?

‍The OWASP Foundation, a global nonprofit supported by volunteers, researchers, and industry practitioners, maintains the OWASP projects and resources.

How often does OWASP update the Top 10?

‍OWASP aims to update its Top 10 projects every few years. For example, the API Security Top 10 was first published in 2019 and updated in 2023.

What is the most difficult API vulnerability to uncover?

‍Business logic flaws, such as those in sensitive workflows, are often the hardest to detect because they require a deep understanding of the application context rather than simple input validation. Automated tools alone rarely catch these issues.

What’s the future of API security?

‍API security will increasingly rely on automation, continuous testing, and integration into CI/CD pipelines. With APIs expanding across cloud, mobile, and microservices, proactive measures like shift-left testing and real-time monitoring will become standard practice.

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