The Ultimate Guide to OWASP API Security Top 10 (2023): Definitions, Examples, Mitigations & Enterprise Strategies

APIs have become the backbone of modern business, driving both operations and revenue. In 2024, analysts reported that API calls accounted for more than 71% of all web traffic. According to a Postman survey, 65% of organizations generate revenue directly from APIs, and 43% of API‑first companies derive over a quarter of their revenue from API consumption. At the same time, API attacks and automated abuse cost enterprises between 94 and 186 billion dollars annually and contribute to 40% of all security incidents. The average global cost of a single data breach is now 4.88 million dollars, rising above 9.3 million in the United States.

APIs are no longer merely technical interfaces; they are critical revenue engines and strategic touchpoints for partners, customers, and AI systems. The financial impact of an API breach extends beyond fines and remediation to lost business, eroded trust, and reputational damage. For CISOs, treating API security as optional places revenue and resilience at risk. Strong, proactive API protection is essential to prevent real financial pain.

What Is the OWASP API Security Top 10?

The Open Web Application Security Project, or OWASP, publishes the API Security Top 10 to highlight the most critical risks facing modern APIs. The 2023 edition synthesizes years of research, incident reports, and real world breaches into ten categories of vulnerabilities. Each category represents a class of weaknesses rather than a single bug, providing a framework to understand and mitigate systemic risk.

The 10 categories are:

• API1: Broken Object Level Authorization (BOLA): Attackers manipulate resource identifiers to access objects they should not, accounting for roughly 40% of API attacks.
• API2: Broken Authentication: Weak or misconfigured authentication enables attackers to impersonate legitimate users.
• API3: Broken Object Property Level Authorization (BOPLA): APIs expose or allow modification of properties that should be protected.
• API4: Unrestricted Resource Consumption: Lack of rate limiting or inefficient queries allows denial of service attacks and excessive resource usage.
• API5: Broken Function Level Authorization: Privileged functions can be invoked without proper access checks.
• API6: Unrestricted Access to Sensitive Business Flows: Critical flows, such as checkout or password reset, can be exploited if unprotected.
• API7: Server Side Request Forgery (SSRF): Unsanitized inputs let attackers make requests from the API server to internal services.
• API8: Security Misconfiguration: Default settings, misconfigured services, or unpatched components create vulnerabilities.
• API9: Improper Inventory Management: Shadow or outdated APIs expose sensitive data and often remain untested.
• API10: Unsafe Consumption of APIs: Blindly trusting third party APIs without validating responses or handling errors can lead to injection or data leakage.

The OWASP API Security Top 10 is not just a reference for security teams. It provides developers, architects, and executives with a structured lens to prioritize investments, strengthen controls, and reduce business risk.

Why the OWASP API Top 10 Matters (As of 2025)

The OWASP API Security Top 10 remains highly relevant in 2025 as APIs become central to business and AI‑driven workflows. Two trends make this more urgent.

• API first adoption is nearly universal. 82% of organisations report an API first mindset, and 74% of developers can publish a new API within a week. APIs are no longer peripheral; they are core products that drive revenue and innovation.
• AI agents are reshaping API consumption. According to the Postman 2025 State of the API report, 89% of developers use generative AI, but only 24% design APIs specifically for AI agent interactions. Over half of organisations already deploy AI agents or plan to within two years. These systems operate at machine scale, issuing thousands of requests per second, continuously and in parallel. Most APIs were designed for human paced usage, leaving them exposed to excessive calls, credential leaks, and sensitive data exposure. 

The OWASP Top 10 categories, particularly Broken Object Level Authorization, Broken Authentication, and Unrestricted Resource Consumption, directly address these risks. Even without a new 2025 release, the 2023 list serves as the de facto benchmark, guiding organisations to secure AI native APIs, manage microservices complexity, and reduce exposure across an expanding attack surface.

The 2023 OWASP API Security Top 10: Deep Dive and Mitigation Strategies

The 2023 OWASP API Security Top 10 provides a clear framework for understanding, prioritising, and mitigating the most critical API risks. Below is a deep dive into each category, why it matters, and recommended mitigation strategies for enterprise adoption.

API1: Broken Object Level Authorization (BOLA)

BOLA occurs when APIs rely on user supplied identifiers without verifying access rights. Attackers manipulate IDs or tokens to access other users’ data, accounting for ~40 % of API attacks.

Mitigation: Enforce fine grained, object level authorization on every request; use unguessable resource IDs; implement context aware access control; monitor abnormal access patterns like sequential ID enumeration.

API2: Broken Authentication

Weak credentials, poor session management, missing MFA, or flawed token handling enable account takeover.

Mitigation: Adopt OAuth 2.0 and OpenID Connect standards; enforce multi-factor authentication; use short lived tokens; rotate secrets regularly; monitor for brute force attacks and credential stuffing.

API3: Broken Object Property Level Authorization (BOPLA)

APIs may expose or allow modification of sensitive object properties, such as, permitting non-admins to set an isAdmin flag.

Mitigation: Apply allowlists on request and response fields; filter out unnecessary or sensitive properties; use schema validation to reject unknown or protected fields.

API4: Unrestricted Resource Consumption

APIs without rate limiting, concurrency controls, or payload restrictions can be exploited for denial of service attacks or resource exhaustion.

Mitigation: Set per method rate limits and quotas; paginate large datasets; monitor spikes in usage; propagate back pressure when calling third party services.

API5: Broken Function Level Authorization

Privileged endpoints may be invoked without proper checks, allowing attackers to perform sensitive operations.

Mitigation: Implement role based and attribute based access controls; segregate endpoints by privilege; validate roles before executing sensitive functions; simulate privilege escalation in security tests.

API6: Unrestricted Access to Sensitive Business Flows

Critical flows like checkout, password reset, or account linking can be abused due to logic flaws or missing context checks.

Mitigation: Harden sensitive flows; enforce multi-step verification; apply contextual checks (rate, IP, device); monitor behavioral anomalies; perform business logic vulnerability scanning and runtime analysis.

API7: Server Side Request Forgery (SSRF)

Attackers trick APIs into making requests to internal or external systems, potentially exposing internal networks.

Mitigation: Validate and sanitize all URLs; enforce allowlists for internal destinations; disable unnecessary network protocols; run services with least privilege; monitor outbound requests.

API8: Security Misconfiguration

Default settings, verbose errors, exposed admin interfaces, and unpatched components create exploitable weaknesses.

Mitigation: Automate configurations via Infrastructure as Code; implement baselines; continuously scan for misconfigurations; securely store secrets; patch and update dependencies regularly.

API9: Improper Inventory Management

Shadow (unknown) and zombie (deprecated) APIs create unmonitored attack surfaces. Enterprises manage thousands of APIs, but manual inventory can track only a fraction of those endpoints.

Mitigation: Maintain a comprehensive API inventory across all environments; automatically discover and catalogue endpoints; track versioning and ownership; decommission unused APIs.

API10: Unsafe Consumption of APIs

Trusting third party APIs without validation exposes injection, data leakage, and privilege escalation risks. 

Mitigation: Validate and sanitize all external data; treat untrusted responses cautiously; implement content security policies; perform contract testing and runtime validation as part of API procurement and integration.

By systematically addressing each category, organisations can reduce the likelihood of breaches, protect sensitive data, and maintain trust while supporting high velocity API first and AI driven operations.

How OWASP Top 10 API Risks Lead to Real Attacks

The vulnerabilities identified in the OWASP API Security Top 10 are not abstract, they directly enable real world attacks with measurable business impact.

• Account Takeovers and Data Theft: BOLA and broken authentication allow attackers to access or modify other users’ data. At scale, AI agents and automated tools can exploit these weaknesses across thousands of requests per second, resulting in breaches, regulatory violations, and reputational damage.
• Service Disruption: Unrestricted resource consumption and SSRF attacks can exhaust servers or networks, causing denial of service events that impact availability, uptime, and customer trust.
• Business Fraud: Broken function level authorization and unprotected business flows allow attackers to manipulate transactions, bypass payment limits, or alter account operations, leading to direct financial losses.
• Credential Leakage: Improper API inventory management and unsafe consumption of APIs expose secrets, tokens, and keys, which attackers can reuse across internal systems, amplifying risk.
• Supply Chain Risk: Integrating third party APIs without proper validation introduces vulnerabilities beyond the organisation’s control, creating systemic exposure across dependent applications.

According to a survey, 84 % of organisations experienced an API security incident, with remediation costs ranging from US $591 k in general industries to US $832 k in financial services. As APIs interconnect more systems and AI agents multiply consumption patterns, these incidents can cascade across ecosystems, amplifying both operational and financial impact.

Why API Security is Harder than it Looks

Securing APIs is fundamentally more complex than securing traditional web applications. Several factors contribute to this unique challenge:

• Exploding Attack Surface: Microservices architectures fragment monoliths into dozens or hundreds of services, each exposing multiple endpoints. For example, breaking a monolith into 40 microservices can increase exposed endpoints by 10–20x. Organisations often manage hundreds of APIs and continually discover additional “shadow” endpoints, expanding the attack surface exponentially.
• Business Logic Complexity: Many API attacks exploit the application’s logic rather than traditional injection vulnerabilities. A 2023 survey found that 27 % of API attacks target business logic. Generic web security tools typically miss these context dependent flaws.
• Machine Scale Consumption: AI agents, webhooks, and IoT devices interact with APIs continuously, in parallel, and with unpredictable patterns. Authentication and rate limiting schemes designed for human paced interactions often fail under this machine scale traffic.
• Invisible Vulnerabilities: Undocumented or untracked APIs remain blind spots for security teams. DAST scanners rely on user interfaces to discover endpoints, while SAST scanners analyze code but cannot capture runtime behavior. APIs without proper cataloguing evade traditional detection methods.
• Legacy Tools and Silos: API gateways handle traffic routing but do not inspect request semantics. WAFs and CDNs can block basic injection attacks but cannot detect BOLA, Broken Function Authorization, or complex business logic flaws.

These challenges make API security a distinct discipline. It cannot be treated as an afterthought or a simple extension of web security. Effective protection requires specialised tools, continuous runtime analysis, and an organisation wide security culture.

How to Protect Against OWASP API Top 10 Risks

Protecting APIs requires a holistic approach that spans design, development, testing, and runtime operations. Key strategies include:

1. Adopt a Shift Left Security Mindset: Integrate security early in the software lifecycle. Conduct threat modelling on new APIs, enforce secure defaults, and implement positive security patterns such as allowlists for objects and properties to reduce exploitable flaws.
2. Build and Maintain an API Inventory: Automatically discover and catalogue all APIs, including internal, third party, shadow, and deprecated endpoints. Leverage traffic analysis, code inspection, and CI/CD integration to ensure the inventory reflects real time deployments.
3. Continuous API Security Testing: Combine static analysis, dynamic testing, fuzzing, protocol aware analysis, and runtime data for comprehensive coverage. Traditional SAST and DAST alone are insufficient.
4. Runtime Monitoring and Threat Detection: Deploy API specific runtime protection to detect and block attacks such as BOLA, brute force attempts, injection, and data exfiltration. Monitor behavioural patterns, context, and payload semantics rather than relying solely on signatures.
5. Rate Limiting and Resource Governance: Enforce per endpoint quotas, concurrency controls, and circuit breakers for expensive operations. Propagate back pressure when calling third party services to prevent cascading failures.
6. Secure Identity and Access Management: Use strong authentication protocols, enforce multi factor authentication, implement fine grained authorization, secure tokens, and rotate secrets regularly.
7. Align with Industry Standards and Best Practices: Follow OWASP API security guidelines, adopt frameworks like Zero Trust, and continuously update practices to address emerging threats and evolving API consumption patterns.

These measures collectively reduce risk, improve resilience, and ensure APIs remain a reliable, secure foundation for modern digital businesses.

Why Traditional API Security Approaches Fail

Many organisations continue to rely on security tools designed for websites and monolithic applications, but these approaches fall short in the API first world:

• SAST Scanners: Static analysis tools review source code but cannot observe runtime flows, sequential calls, or distributed interactions. They generate false positives and often miss business logic vulnerabilities or data flow issues across microservices.
• DAST Scanners: Dynamic testing relies on crawling user interfaces and known URLs. APIs lack a UI and require awareness of endpoints, parameters, and authentication. DAST cannot discover hidden or sequential endpoints and depends on incomplete documentation.
• API Gateways and WAFs: While effective against standard web attacks like SQL injection and XSS, gateways and WAFs cannot enforce object level authorization or interpret API semantics. They operate at the network layer without visibility into business logic or context specific rules.
• Manual Penetration Testing: Pen tests are necessary but infrequent. Human testers cannot keep pace with agile releases, microservices, or AI driven API consumption patterns.

Securing APIs with traditional web tools leaves significant gaps. Enterprises need specialised solutions that understand API behaviour, runtime context, and payload semantics to protect against modern threats.

Continuous API Security Testing: The Missing Layer

Traditional pre deployment scans and runtime protections are not enough. Continuous API security testing bridges this gap and ensures APIs remain secure throughout their lifecycle.

Continuous testing guarantees that new endpoints, modified parameters, and authentication updates are automatically verified, closing gaps that traditional security approaches leave open.

• Combining Static, Dynamic, and Runtime Feedback: Leverage static analysis to identify insecure code patterns, dynamic testing to exercise endpoints, and fuzzers to uncover unexpected behaviours. Incorporate runtime telemetry to refine test cases and detect real world attack vectors.
• Automated Test Generation: Create API specific tests covering object level authorization, input validation, rate limiting, and business logic. Automation reduces reliance on manual testing and ensures comprehensive coverage across all endpoints.
• Integration into CI/CD Pipelines: Embed security tests into every build, release, and code change. 
• Zero Noise Prioritisation: Focus on exploitable risks and actual data exposure instead of theoretical issues. High signal, low noise findings accelerate remediation and improve developer trust in security feedback.

How Levo Helps You Address the OWASP API Top 10

Levo.ai is built to tackle the unique challenges of API security across the entire lifecycle, from discovery and testing to runtime protection, while mapping directly to each OWASP category.

Proactive Module: Visibility and Testing

• API Inventory and Documentation: Levo automatically discovers all internal, external, shadow, and deprecated APIs, generating rich, traffic based documentation. This directly mitigates API9 (Improper Inventory Management) by ensuring no endpoints operate unseen.
• Sensitive Data Discovery: The platform maps sensitive data flows, highlighting where personal, financial, or secret information traverses APIs. This supports OWASP API 6 and OWASP API 10 by ensuring sensitive business flows are monitored and controlled.
• Security Testing and BOLA/BOPLA Detection: Levo performs comprehensive testing for BOLA and BOPLA. For OWASP API 1, it verifies object level authorization on every endpoint; for OWASP API 3, it detects broken property level access and enforces context aware controls.
• Authentication Testing: For OWASP API 2, Levo identifies authentication schemes per endpoint, tests for weaknesses, and flags broken or missing authentication. It supports OAuth, JWT, API keys, and monitors token misuse.
• Rate Limiting and Resource Testing: For API4, Levo tests endpoints under high load, identifies exhaustion risks, and provides remediation guidance, simulating AI scale traffic patterns to reveal vulnerabilities.
• Sensitive Business Flow Analysis: For API6, Levo maps critical flows like checkout and account resets, simulating misuse to ensure multi-factor and context aware checks are enforced.

Governance Module: Monitoring and Threat Detection

• Real Time Monitoring: Runtime sensors (via eBPF) monitor all API traffic without ingesting payloads. Levo detects abnormal patterns such as sequential ID access (BOLA), brute force attacks (OWASP API 2), excessive consumption (OWASP API 4), or misuse of flows (OWASP API 6). Continuous monitoring covers OWASP API 7 to OWASP API 10, detecting misconfigurations, SSRF attempts, shadow APIs, and unsafe third party integrations.
• Threat Detection and Alerting: High fidelity behavioral analysis surfaces actionable threats with low false positives. Alerts include risk scores, context, and recommended responses. Custom threat rules allow coverage for emerging or industry specific attack patterns.

Runtime Module: Detection and Blocking

• Inline Protection: Levo blocks attacks in real time, enforcing object level authorization, validating tokens, rate limiting abusive calls, and dropping malicious SSRF or injection attempts.
• Custom Blocking Rules and CVE Coverage: Security teams can define bespoke rules for known CVEs or organization specific logic flaws. Levo provides pre-built coverage for OWASP API threats while remaining adaptable to custom cases.

By combining proactive discovery and testing, governance level monitoring, and runtime protection, Levo delivers full OWASP API Top 10 coverage. Each module builds on the previous, ensuring vulnerabilities are detected early, continuously monitored, and blocked before exploitation.

The Way Ahead: Protecting Against OWASP API Security Top 10 Threats Requires a Holistic Approach

APIs now power revenue, AI agents and entire digital ecosystems. With this growth comes greater exposure to data, logic and infrastructure risks. The OWASP API Security Top 10 highlights the most critical threats, but awareness alone is not enough. True protection requires a comprehensive, lifecycle wide strategy that evolves with how modern APIs are built and consumed.

• Shift Left and Shift Right: Security must be built into both development and operations. Secure design, coding practices and continuous testing catch issues early, while runtime observability and inline protection detect and block real attacks in production. This dual strategy ensures both preventive and defensive coverage.
• Unify Security and Business Objectives: API security is fundamentally a revenue protection function. Prioritise initiatives using business metrics such as downtime impact, revenue at risk and compliance exposure. This alignment strengthens investment decisions and ensures security becomes a business enabler, not a bottleneck.
• Prepare for AI Native Consumption: APIs must be ready for machine scale usage. High concurrency, automated workflows and non human patterns demand adaptive rate limits and AI driven anomaly detection. Designing with AI consumption in mind reduces operational risk and future proofs the API ecosystem.
• Leverage Platform Solutions: Point tools alone cannot secure complex, distributed API environments. Platforms like Levo that unify discovery, documentation, testing, monitoring and protection simplify operations and provide full lifecycle coverage. This consolidation reduces gaps, noise and integration overhead.

By adopting these principles, organisations can transform API security from a reactive burden into a strategic advantage. A secure API landscape accelerates innovation, strengthens trust and unlocks the full economic potential of an API driven digital enterprise.

Effective testing ensures innovation doesn’t come at the cost of exposure, and that speed never compromises safety. Platforms like Levo.ai make this possible by automating API security from design to runtime, turning protection into a continuous process rather than a reactive one.

Levo.ai doesn’t just detect vulnerabilities; it actively safeguards APIs as they evolve. For organizations operating at scale, now is the time to modernize your testing strategy. 

Shift left, automate early, and secure continuously. That’s how resilient API security and sustainable innovation are built.

Levo delivers seamless OWASP API Security against Top 10 Vulnerabilities for modern organisations. Book your demo today to implement API security.