---
title: "OWASP API Security Top 10: Cheat Sheet & Fixes (2026)"
description: "OWASP API Security Top 10 explained: BOLA, broken auth, mass assignment, rate limiting, SSRF — with practical fixes and code examples for production APIs."
canonicalUrl: "https://zuplo.com/learning-center/owasp-cheat-sheet-guide"
pageType: "learning-center"
authors: "adrian"
tags: "API Security"
image: "https://zuplo.com/og?text=OWASP%20API%20Security%20Top%2010%3A%20Cheat%20Sheet%20%26%20Fixes%20(2026)"
---
API security has become a critical concern for businesses of all sizes. With
organizations increasingly relying on APIs to power their applications and
services, robust security measures are essential. The
[OWASP API Security Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/REST_Security_Cheat_Sheet.html)
offers invaluable guidance to help secure APIs, protect sensitive data, maintain
user trust, and meet industry standards and regulatory requirements.

API-based attacks are on the rise, with the
[OWASP API Security Top 10](https://owasp.org/www-project-api-security/)
identifying broken object-level authorization and broken authentication as the
top two API security risks. This growing threat landscape requires organizations
to align with established security best practices to mitigate risks while
maintaining development efficiency. This approach allows teams to focus on
innovation without compromising security.

The API security landscape constantly evolves. In this article, we'll explore
essential API security concepts, examine OWASP's recommendations, and discuss
best practices to create secure, high-performing APIs.

## OWASP API Security Top 10 Quick Reference

Here is a quick-reference mapping each OWASP API Security Top 10 risk to a
practical fix and the Zuplo policy that addresses it at the gateway level:

- **API1 — Broken Object Level Authorization (BOLA)**: Enforce per-resource
  ownership checks on every endpoint. Use Zuplo's
  [Custom Code Inbound policy](/docs/policies/custom-code-inbound) to validate
  `request.user.sub` against the resource owner before returning data.
- **API2 — Broken Authentication**: Require verified tokens on every request.
  Use Zuplo's [JWT Auth policy](/docs/policies/open-id-jwt-auth-inbound) or
  [API Key Authentication](/docs/policies/api-key-inbound) to validate
  credentials before they reach your backend.
- **API3 — Broken Object Property Level Authorization**: Strip or validate
  sensitive fields in request and response bodies. Use Zuplo's
  [Custom Code Outbound policy](/docs/policies/custom-code-outbound) to filter
  response properties, or
  [Request Validation](/docs/policies/request-validation-inbound) to reject
  unexpected input fields.
- **API4 — Unrestricted Resource Consumption**: Cap request rates per consumer.
  Use Zuplo's [Rate Limiting policy](/docs/policies/rate-limit-inbound) with
  `rateLimitBy: "user"` to enforce per-consumer limits and return `429` when
  thresholds are exceeded.
- **API5 — Broken Function Level Authorization**: Restrict admin and privileged
  endpoints by role. Use Zuplo's
  [RBAC Authorization policy template](/docs/policies/rbac-policy-inbound) or
  [JWT Scope Validation policy](/docs/policies/jwt-scopes-inbound) to verify
  callers have the required permissions.
- **API6 — Unrestricted Access to Sensitive Business Flows**: Detect and block
  automated abuse of business-critical workflows. Use Zuplo's
  [Rate Limiting policy](/docs/policies/rate-limit-inbound) combined with
  [Custom Code Inbound](/docs/policies/custom-code-inbound) to add
  business-logic checks such as velocity limits or CAPTCHA enforcement.
- **API7 — Server-Side Request Forgery (SSRF)**: Validate and allowlist all
  outbound URLs in user-supplied input. Use Zuplo's
  [Custom Code Inbound policy](/docs/policies/custom-code-inbound) to sanitize
  URL parameters and reject requests targeting internal networks.
- **API8 — Security Misconfiguration**: Enforce HTTPS, proper CORS, and remove
  unnecessary headers. Use Zuplo's [CORS configuration](/docs/articles/cors),
  [Remove Request Headers policy](/docs/policies/remove-headers-inbound), and
  [WAF and DDoS options](/docs/articles/waf-ddos) to harden your gateway.
- **API9 — Improper Inventory Management**: Document every endpoint via OpenAPI
  and gate access by environment. Use Zuplo's
  [built-in Developer Portal](/docs/dev-portal/introduction) to auto-generate
  docs from your OpenAPI spec, keeping your API inventory discoverable and
  up-to-date.
- **API10 — Unsafe Consumption of APIs**: Validate and sanitize all data
  received from third-party APIs. Use Zuplo's
  [Request Validation policy](/docs/policies/request-validation-inbound) on
  outbound calls and [Custom Code Outbound](/docs/policies/custom-code-outbound)
  to verify responses before forwarding them to clients.

## Understanding API Security Basics with The OWASP API Security Cheat Sheet

API security is the practice of protecting APIs from unauthorized access,
malicious attacks, and data breaches. As APIs have become fundamental components
of modern software architecture,
[using APIs responsibly](/learning-center/espn-hidden-api-guide) and securing
them has become critically important for maintaining user trust and protecting
sensitive data. The
[OWASP REST Security Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/REST_Security_Cheat_Sheet.html)
provides essential guidelines to address these concerns effectively.

### Definition of API Security

API security encompasses measures designed to safeguard the integrity,
confidentiality, and availability of APIs. It involves implementing
authentication, authorization, encryption, and monitoring mechanisms to ensure
that only authorized users and applications can access API endpoints.

### Common API Security Threats

Several security threats plague APIs, making them attractive targets for
attackers:

- **Broken Object Level Authorization (BOLA)**: APIs fail to properly verify
  that a user is authorized to access specific resources. An attacker might
  access another user's data by simply modifying object identifiers in API
  requests.
- **Broken Authentication**: Poor implementation of authentication mechanisms
  can allow attackers to compromise tokens or exploit flaws to impersonate
  legitimate users.
- **Excessive Data Exposure**: APIs may inadvertently expose sensitive data by
  returning more information than necessary in responses.
- **Injection Attacks**: Malicious input can manipulate API behavior,
  potentially leading to unauthorized data access or system compromise.
- **Improper Asset Management**: Outdated or poorly documented APIs can create
  security vulnerabilities if left unmanaged.

### Importance of Proactive Security Measures

Implementing proactive security measures is crucial for protecting APIs from
these threats and is a key component of effective
[API lifecycle management](/learning-center/api-lifecycle-strategies). According
to the
[OWASP API Security Project](https://owasp.org/www-project-api-security/), a
reactive approach to API security just doesn't cut it anymore.

Proactive security measures include:

- Implementing robust authentication and authorization checks consistently
  across all API endpoints.
- Enforcing strict input validation and sanitization to prevent injection
  attacks.
- Using encryption for data in transit and at rest to protect sensitive
  information, reinforcing
  [data protection and security](/learning-center/building-apis-to-monetize-proprietary-data).
- Regularly auditing and updating API documentation and access controls.
- Monitoring API usage for suspicious activity and implementing rate limiting to
  prevent abuse.

API security best practices don't have to be complex. Modern API management
platforms allow developers to implement security measures directly in their
code, rather than through complex configurations. This code-first approach
integrates security seamlessly into development workflows, ensuring security is
built into APIs from the ground up.

## Overview of The OWASP API Security Cheat Sheet

The
[OWASP REST Security Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/REST_Security_Cheat_Sheet.html)
is a cornerstone resource for API security, giving developers, tech leads, and
security professionals a practical guide to securing their APIs. This tool is
part of the larger
[OWASP Cheat Sheet Series](https://cheatsheetseries.owasp.org/), which provides
practical guidance on various application security topics.

### Purpose and Authority

The OWASP REST Security Cheat Sheet offers clear, actionable advice for
addressing the unique security challenges of modern APIs. It turns complex
security requirements into practical steps, making it an essential reference for
teams at all stages of API development.

OWASP's authority in application security is unmatched, with over two decades of
community-driven expertise behind its recommendations. This collective knowledge
ensures the cheat sheet addresses real-world challenges, not just theoretical
concepts.

### Understanding Cheat Sheets

OWASP cheat sheets are practical tools for implementing complex security
protocols. They connect high-level security principles with concrete
implementation details. For API security, this means specific guidance on issues
like:

- **Transport Layer Security**: The
  [REST Security Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/REST_Security_Cheat_Sheet.html)
  emphasizes that "Secure REST services must only provide HTTPS endpoints" to
  protect authentication credentials in transit.
- **Authentication Mechanisms**: Detailed advice on secure password handling,
  token-based authentication, and multi-factor authentication is provided,
  aligning with best practices outlined in the
  [OWASP Authentication Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html).
- **Authorization**: The cheat sheet stresses the importance of implementing
  proper object-level and
  [function-level authorization](./2025-07-30-troubleshooting-broken-function-level-authorization.md)
  to prevent common vulnerabilities like
  [Broken Object Level Authorization (BOLA)](./2025-07-27-troubleshooting-broken-object-level-authorization.md).
- **Input Validation**: Guidance on validating and sanitizing all input to
  prevent injection attacks and other security risks is a key focus.
- **Error Handling**: Recommendations for secure error handling that doesn't
  expose sensitive information to potential attackers.
- **Rate Limiting**: Strategies for implementing rate limiting to protect
  against abuse and denial-of-service attacks.

The structured approach of The
[OWASP API Security Top 10](https://owasp.org/www-project-api-security/)
provides a methodical way to address critical API security risks. This framework
helps development teams prioritize their security efforts, focusing on
high-impact areas first.

## Core Security Measures Recommended by The OWASP API Security Cheat Sheet

The OWASP REST Security Cheat Sheet provides comprehensive guidance on
implementing robust security measures for your APIs. Let's explore the
fundamental security controls recommended by OWASP and how you can effectively
implement them.

### Authentication and Authorization

Proper authentication and authorization are critical for protecting your API
from unauthorized access and are central to
[API management best practices](/learning-center/monetize-ai-models):

- Use secure authentication protocols like OAuth 2.0 or OpenID Connect.
- Implement multi-factor authentication for sensitive operations.
- Enforce proper object-level and function-level authorization checks.

For example, when implementing object-level authorization:

```python
@app.route('/api/records/<record_id>', methods=['GET'])
@jwt_required
def get_record(record_id):
    current_user = get_jwt_identity()
    record = Record.query.get(record_id)

    if not record:
        return jsonify({"error": "Record not found"}), 404

    if record.owner_id != current_user and not user_has_admin_role(current_user):
        logging.warning(f"User {current_user} attempted unauthorized access to record {record_id}")
        return jsonify({"error": "Not authorized to access this record"}), 403

    return jsonify(record.to_dict()), 200
```

This example demonstrates proper authorization checks, ensuring that only the
record owner or an admin can access the data.

### Data Validation and Encoding

To prevent injection attacks and other data-related vulnerabilities, it is
crucial to
[implement security features](/blog/adding-dev-portal-and-request-validation-firebase)
such as:

- Validate all input parameters for length, format, and type.
- Use strong typing and restrict string inputs with regular expressions.
- Implement server-side validation in addition to any client-side checks.
- Sanitize and encode all output to prevent XSS attacks.

### Data Encryption

Protecting sensitive data both in transit and at rest is crucial:

- Use HTTPS for all API communication to encrypt data in transit.
- Implement proper encryption for sensitive data stored in databases.
- Use strong, up-to-date encryption algorithms and key management practices.

To enforce HTTPS usage, you can implement strict transport security headers:

```python
from flask import Flask

app = Flask(__name__)

@app.after_request
def add_security_headers(response):
    response.headers['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains'
    return response
```

This code adds the Strict-Transport-Security header to all responses,
instructing browsers to always use HTTPS for your API.

## Advanced Security Controls

When it comes to API security, basic measures are just the starting point.
Advanced security controls protect against sophisticated threats.

### Rate Limiting and Throttling

Rate limiting and throttling prevent abuse and protect your API from
denial-of-service (DoS) attacks. These controls keep your API available and
responsive, even under heavy load or during attacks.

To implement effective rate limiting:

- Set appropriate limits based on your API's capacity and expected usage.
- Use a sliding window algorithm for more precise control.
- Return a 429 (Too Many Requests) HTTP status code when limits are exceeded.
- Provide clear documentation on rate limits for your API consumers.

You can check out our
[full guide to understanding and building API rate limiting](/learning-center/api-rate-limiting)
to learn more about best practices for rate limit design and implementation.

### Monitoring and Logging

Comprehensive [monitoring and logging](/blog/tour-of-the-portal), utilizing
effective
[API monitoring tools](/learning-center/8-api-monitoring-tools-every-developer-should-know),
help detect and respond to security incidents. These practices give you insights
into your API's usage patterns and potential security threats.

Key aspects of effective monitoring and logging include:

- Tracking authentication failures, issues with
  [authorization mechanisms](/learning-center/rbac-analytics-key-metrics-to-monitor),
  and input validation errors.
- Monitoring for unusual access patterns or traffic spikes.
- Logging all API requests and responses for auditing.
- Implementing real-time alerting for critical security events.

### Security Testing and Audits

Regular security testing and audits identify vulnerabilities before they become
major problems. Incorporating these practices into your development workflow
helps catch potential issues early.

Consider implementing:

- Automated security scanning as part of your CI/CD pipeline.
- Regular penetration testing by security experts.
- Code reviews focused on security best practices.
- Periodic security audits to assess overall API security.

## Implementation Strategies Using The OWASP API Security Cheat Sheet

Implementing The
[OWASP REST Security Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/REST_Security_Cheat_Sheet.html)
recommendations requires integrating security throughout the API development
lifecycle, including in your
[API deployment strategies](/learning-center/accelerating-developer-productivity-with-federated-gateways)
and leveraging effective
[API management solutions](https://zuplo.com/api-gateways/tyk-api-management-alternative-zuplo).

### Design Phase Security Considerations

When designing your API, making informed
[infrastructure choices](/learning-center/hosted-api-gateway-advantages) and
incorporating security requirements based on The OWASP REST Security Cheat Sheet
recommendations is essential. Start with threat modeling exercises like STRIDE
to identify where specific controls are most needed.

Consider adopting security stories in your Agile sprints:

"As a developer, I will implement input validation for all API parameters using
regular expressions to prevent injection attacks."

This approach treats security as a functional requirement rather than an
afterthought.

### Integrating Security in Development Cycles

During development, enforce coding standards that align with OWASP
recommendations:

- Mandate input validation and sanitization using recommended libraries.
- Implement secure authentication and authorization mechanisms as outlined in
  the
  [OWASP Authentication Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html).
- Integrate security unit tests that check for parameter boundary conditions and
  proper output encoding.

Embed security checks into your CI/CD pipeline:

- Run API security scanners like [OWASP ZAP](https://www.zaproxy.org/) as part
  of your build and testing process.
- Configure your pipeline to fail builds if high-severity vulnerabilities or
  OWASP Top 10 issues are detected.

## Gap Opportunities and Enhancements in API Security

As API security evolves, new methodologies, tools, and strategies are emerging
to address changing threats. Organizations need to stay ahead of these
developments to maintain strong API security and build secure API environments.

### Emerging Trends in API Security

**Zero Trust Architecture** is gaining momentum in API security. This approach
goes beyond traditional perimeter-based security models by requiring
verification for every request, regardless of origin.

**Shift-Left Security** is becoming standard in API development. Rather than
treating security as an afterthought, this approach integrates security
considerations early in the development process.

### Leveraging Machine Learning and AI

AI and Machine Learning are transforming API security practices, enhancing
threat detection and response:

- **Anomaly Detection**: AI systems analyze API traffic patterns to identify
  unusual behavior that may indicate security threats.
- **Automated Threat Response**: Machine learning algorithms can automatically
  respond to certain security incidents, reducing the burden on security teams.
- **Predictive Analysis**: AI helps predict potential API vulnerabilities based
  on historical data and emerging threat patterns. For example, tools like
  [**RateMyOpenAPI**](https://ratemyopenapi.com) uses a mix of AI and heuristics
  to identify security issues in your API specification and suggests fixes.
- **Intelligent Rate Limiting**: Machine learning dynamically adjusts rate
  limits based on user behavior and API usage patterns.

To stay current with these emerging trends and technologies, organizations
should regularly review and update their API security strategies. The
[OWASP API Security Project](https://owasp.org/www-project-api-security/)
provides valuable guidance on implementing these advanced security measures.

## Strengthening Your API Security with OWASP Best Practices

The OWASP REST Security Cheat Sheet offers vital guidance for securing APIs in
today’s threat-heavy environment. Core practices like strong authentication,
input validation, encryption, rate limiting, and monitoring help reduce exposure
to common attacks.

Maintaining robust API security also requires ongoing effort: updating controls
for new threats, integrating security into CI/CD pipelines, training development
teams, and applying a defense-in-depth strategy in line with OWASP
recommendations.

By adopting these best practices, organizations can build APIs that are secure,
resilient, and capable of delivering outstanding digital experiences—while also
protecting critical data and reducing the long-term costs of breaches.

For deeper dives into specific areas covered by OWASP, check out these related
guides:

- [Zero Trust API Security](/learning-center/zero-trust-api-security) — how to
  implement a verify-every-request model that aligns with OWASP's authorization
  guidance.
- [Securing APIs Against Broken Authentication Vulnerabilities](/learning-center/securing-apis-against-broken-authentication-vulnerabilities)
  — detailed strategies for addressing API2 (Broken Authentication).
- [Practices and Tools to Ensure API Security](/learning-center/practices-and-tools-to-ensure-api-security)
  — a broader look at the tools and workflows that support OWASP-aligned
  security postures.

Still, putting these practices into action can be challenging without the right
tools. That’s where Zuplo comes in. Our API gateway helps you enforce
OWASP-aligned protections—like authentication, rate limiting, and
monitoring—right out of the box. Let Zuplo handle the security heavy lifting so
your team can focus on building great products —
[try it for free today](https://portal.zuplo.com/signup?utm_source=blog)!