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# System prepended metadata

title: OWASP API Security Top 10

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# **OWASP API  top 10**

APIs are the backbone of modern applications, but their exposure to the internet makes them a prime target for attacks. The **OWASP API Security Top 10** outlines the most critical API vulnerabilities and how to mitigate them.

## **1. Broken Object Level Authorization (BOLA)**

When an API fails to properly enforce authorization, a user can access or modify another user's data.

🔹 **Example:**

- A banking API allows user A to access their transactions using `/transactions/12345`.
- User B modifies the request to `/transactions/67890` and retrieves someone else's transaction history.

🔹 **Mitigation:**

- Implement **strict access controls** at the object level.
- Verify user permissions for every API request.

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## **2. Broken Authentication**

Weak authentication or missing security controls allow attackers to bypass login mechanisms.

🔹 **Example:**

- An API allows logins with only an **email and a weak password** without rate limiting or MFA.
- An attacker brute-forces accounts using leaked passwords.

🔹 **Mitigation:**

- Enforce **strong authentication (OAuth, JWT, MFA)**.
- Implement **rate limiting** to prevent brute-force attacks.

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## **3. Broken Object Property Level Authorization**

APIs expose or allow modification of sensitive data through insecure endpoints.

🔹 **Example:**

- A user sends a request to update their profile:
    
    ```json
    { "name": "John", "role": "admin" }
    ```
    
- The API accepts it, granting admin privileges.

🔹 **Mitigation:**

- Restrict access to **sensitive fields** at both request and response levels.
- Enforce **backend validation** to prevent unauthorized modifications.

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## **4. Unrestricted Resource Consumption**

APIs that lack resource limits are vulnerable to abuse, leading to **Denial of Service (DoS)**.

🔹 **Example:**

- A bot sends **millions of requests per second**, crashing the API.

🔹 **Mitigation:**

- Implement **rate limiting, request throttling, and quota enforcement**.
- Optimize database queries to **handle high loads efficiently**.

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## **5. Broken Function Level Authorization**

APIs expose **administrative functionalities** to regular users, allowing **privilege escalation**.

🔹 **Example:**

- A user modifies an API request from `GET /user/profile` to `DELETE /user/1234`, deleting someone else's account.

🔹 **Mitigation:**

- Enforce **role-based access control (RBAC)**.
- Use **least privilege** principles for API endpoints.

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## **6. Unrestricted Access to Sensitive Business Flows**

Attackers exploit business processes through excessive automation.

🔹 **Example:**

- A travel booking API allows unlimited ticket reservations, leading to fraudulent activity.

🔹 **Mitigation:**

- Implement **CAPTCHAs, behavior-based monitoring, and anomaly detection**.

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## **7. Server-Side Request Forgery (SSRF)**

APIs that fetch external resources based on user input can be tricked into making requests to internal systems.

🔹 **Example:**

- An attacker submits `http://localhost/admin` to an API that fetches URLs, exposing internal services.

🔹 **Mitigation:**

- Restrict external requests to **trusted domains**.
- Validate and sanitize user inputs.

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## **8. Security Misconfiguration**

Improper API settings expose systems to attacks.

🔹 **Example:**

- A misconfigured API exposes **debugging endpoints** that reveal sensitive data.
- **CORS misconfiguration** allows unauthorized domains to access API resources.

🔹 **Mitigation:**

- Disable **unnecessary features** (e.g., verbose error messages, debug modes).
- Implement **secure default configurations** and **regular security patches**.

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## **9. Improper Inventory Management**

Exposed, outdated, or undocumented API versions create security risks.

🔹 **Example:**

- An old API endpoint (`/v1/user-data`) remains active while `/v2/user-data` is introduced, allowing attackers to exploit legacy weaknesses.

🔹 **Mitigation:**

- Maintain **an up-to-date API inventory**.
- **Retire old APIs** and remove unused endpoints.

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## **10. Unsafe Consumption of APIs**

Trusting third-party APIs blindly can introduce vulnerabilities.

🔹 **Example:**

- An API integrates with an external service that **stores data insecurely**, leading to leaks.

🔹 **Mitigation:**

- Validate and sanitize **all responses from third-party APIs**.
- Use **API security gateways** to filter malicious responses.

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# **Pillars of API Security**

To build **secure APIs**, organizations must focus on:

### **1️⃣ Governance (Secure API Development)**

🔹 Establish **security policies and design guidelines**.  
🔹 Ensure **consistent security practices** throughout API development.

### **2️⃣ Testing (Finding API Vulnerabilities)**

🔹 **Automate security testing** (fuzzing, injection, access control checks).  
🔹 Test for **business logic flaws** and **API function abuse**.

### **3️⃣ Monitoring (Detecting Threats in Production)**

🔹 Use **runtime protection** to filter traffic.  
🔹 Detect and respond to **API abuse and distributed attacks**.

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# **OpenAPI Specification (Swagger) for Secure API Documentation**

Using **OpenAPI (Swagger)** helps ensure:  
✅ **Standardized API documentation**.  
✅ **Security policies** (authentication, rate limits).  
✅ **Consistent endpoint structures**.

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# **Conclusion**

APIs are critical but **high-risk attack surfaces**. Understanding the **OWASP API Security Top 10** and implementing **best security practices** helps prevent breaches and protect sensitive data. 🚀