In today’s rapidly evolving digital landscape, APIs (Application Programming Interfaces) play a crucial role in enabling communication between different software applications. Ensuring the security and reliability of these APIs is paramount to prevent vulnerabilities and protect sensitive data. This blog will guide you through using Playwright & TypeScript for advanced API security testing, highlighting the importance of automated testing in maintaining robust APIs. 

Introduction to Playwright & TypeScript


Playwright is a powerful end-to-end testing framework developed by Microsoft. It allows you to automate browser actions, making it an excellent tool for testing web applications. Playwright supports multiple browsers (Chromium, Firefox, and WebKit) and provides a robust API for scripting complex interactions. 


TypeScript is a statically typed superset of JavaScript that compiles to plain JavaScript. It offers type safety, improved developer experience, and early error detection, making it an ideal choice for large-scale applications and complex testing scenarios.

Understanding Security Testing

Security Testing involves evaluating a system or application’s security mechanisms to identify vulnerabilities, threats, and risks. The primary goal is to ensure that the system’s data and resources are protected from unauthorized access or breaches. 

Types of Security Testing;

  1. Vulnerability Scanning: Automated scans to detect vulnerabilities. 
  2. Penetration Testing: Simulating attacks to find exploitable vulnerabilities. 
  3. Security Audits: Reviewing code and configuration for security flaws. 
  4. Risk Assessment: Identifying and evaluating potential security risks. 
  5. Ethical Hacking: Authorized attempts to exploit security weaknesses. 
  6. Posture Assessment: Evaluating the overall security readiness of an organization. 

The Need for API Security Testing

APIs are crucial for modern applications, enabling communication between different services. However, they are also prime targets for attackers due to their accessibility and the sensitive data they often handle. 

Reasons for API Security Testing:

  1.  Prevent Data Breaches: APIs often handle sensitive data. Security testing ensures this data remains protected. 
  2. Ensure Compliance: Many industries have regulatory requirements for data protection (e.g., GDPR, HIPAA). 
  3. Protect Business Reputation: Security breaches can damage a company’s reputation and erode customer trust. 
  4. Safeguard Against Attacks: APIs can be vulnerable to various attacks such as SQL injection, XSS (Cross-Site Scripting), and CSRF (Cross-Site Request Forgery). 
  5. Secure Integration: APIs often connect various parts of a system. Ensuring their security is essential for overall system integrity. 

Common API Security Vulnerabilities

  • SQL Injection (SQLi): SQL injection is a code injection technique that allows attackers to execute arbitrary SQL queries. It can lead to unauthorized data access, data breaches, and data manipulation. 
  • Cross-Site Scripting (XSS): XSS vulnerabilities enable attackers to inject malicious scripts into web pages viewed by other users. These scripts can steal session cookies, manipulate page content, and perform phishing attacks. 
  • Cross-Site Request Forgery (CSRF): CSRF attacks trick users into performing unauthorized actions on a web application where they are authenticated. This can lead to unintended data changes, such as password changes or financial transactions. 

How to Perform Security Testing Manually

Manual Security Testing Process:

  1. Exploratory Testing: 
    • Description: Testers manually explore the API’s functionalities, endpoints, and inputs to identify potential security vulnerabilities. 
    • Approach: They simulate different user behaviors and inputs to uncover security weaknesses such as injection flaws or improper authentication mechanisms. 
    • Tools: No specific tools are mandated, but testers often use manual exploration techniques and basic HTTP clients like Curl or Postman. 
  2. Crafting Requests: 
    • Description: Testers manually construct API requests with various parameters and payloads to probe for vulnerabilities. 
    • Objective: They aim to trigger unexpected behavior or expose vulnerabilities such as SQL injection, XSS, or sensitive data exposure. 
    • Tools: Tools like Burp Suite may assist in crafting and modifying requests to test different attack vectors. 
  3. Analyzing Responses: 
    • Description: Testers manually examine API responses for anomalies or indications of security weaknesses. 
    • Focus: They scrutinize response headers, payloads, and status codes to detect issues like improper error handling or data leakage. 
    • Tools: Manual inspection tools and scripts may aid in analyzing responses for patterns indicative of vulnerabilities. 
  4. Using Tools: 
    • Description: Testers leverage specialized tools like Burp Suite, OWASP ZAP, or Postman for more structured testing and vulnerability detection. 
    • Activities: They perform tasks such as intercepting traffic, fuzzing inputs, and validating against security best practices and standards. 
    • Outcome: Identified vulnerabilities are manually verified, prioritized, and documented for remediation. 


  • Human Intuition: Enables testers to apply creativity and intuition to uncover complex, non-obvious vulnerabilities that automated tools may miss. 
  • Comprehensive Understanding: Provides deep insights into the API’s behavior, logic flaws, and potential security blind spots that automated tests might overlook. 


  •  Time-Consuming: Testing large or complex APIs manually can be labor-intensive and slow, hindering scalability for extensive testing. 
  • Error-Prone: Subject to human error, leading to inconsistent test coverage and potentially missing critical vulnerabilities. 
  • Limited Scalability: Challenging to scale for larger applications or frequent testing cycles due to resource-intensive manual efforts. 

How to Perform Security Testing with Automation

Automated Security Testing Process:

  1. Setting Up Automation Frameworks: 
    • Description: Engineers configure automation frameworks like Playwright & TypeScript to script security tests for APIs. 
    • Configuration: Playwright & TypeScript framework setup includes defining test scenarios, integrating with version control, and establishing execution environments. 
    • Tools: Utilizes Playwright’s capabilities for browser automation and interaction with web applications. 
  2. Scripting Tests: 
    • Description: Engineers write scripts to automate security tests such as vulnerability scans, penetration tests, and validation of security controls. 
    • Execution: Scripts simulate attack scenarios (e.g., SQL injection attempts, XSS payloads) across API endpoints to identify vulnerabilities. 
    • Coverage: Automated tests encompass a wide range of scenarios, including edge cases and standardized attacks, ensuring thorough coverage. 
  3. Continuous Testing: 
    • Description: Integration of automated tests into CI/CD pipelines facilitates continuous validation of API security with every code change or deployment. 
    • Benefits: Ensures early detection of vulnerabilities, facilitates quick feedback loops, and supports agile development practices. 
    • Tools: CI/CD tools like Jenkins or GitLab CI/CD orchestrate automated test execution and integration with development workflows. 
  4. Analyzing Results: 
    • Description: Automated tools automatically analyze test results, generate detailed reports, and prioritize identified vulnerabilities based on severity. 
    • Insights: Reports provide actionable insights, highlighting vulnerabilities, and recommending mitigation strategies. 
    • Integration: Results feed into development dashboards, enabling stakeholders to track security posture and prioritize remediation efforts. 


  •  Efficiency: Automated tests execute quickly and consistently, enabling rapid iteration and coverage of multiple API endpoints and scenarios. 
  • Reliability: Reduces the risk of human error, ensuring consistent security validation without variability in test execution. 
  • Comprehensive Coverage: Covers a broad spectrum of attack vectors and scenarios, including repetitive tasks and edge cases often missed by manual testing. 
  • Scalability: Easily scales to accommodate large-scale applications, frequent testing cycles, and evolving security requirements. 
  • Cost-Effectiveness: While the setup may be initially complex, automated testing minimizes long-term costs by reducing manual effort and detecting issues early in the development lifecycle. 


  • Setup Complexity: Initial configuration and scripting require specialized knowledge and time investment, especially for complex APIs and environments.
  • Limitations in Complexity: Automated tools may struggle to identify intricate logic flaws or zero-day vulnerabilities requiring nuanced human analysis and understanding. 

Setting Up Playwright with TypeScript

1. Initialize the Project:

2. Install Dependencies: 

3. Configure TypeScript: 

Create a `tsconfig.json` file: 

4. Directory Structure: 

   Create a `src` directory and an `index.ts` file inside it. 

Implementing Security Tests with Playwright:

Example: Testing for SQL Injection

Understanding SQL Injection Payloads:

  • SQL Injection is a common web security vulnerability that allows attackers to interfere with the queries executed on a database. Attackers can exploit this vulnerability by injecting malicious SQL code into an input field, tricking the application into executing unintended SQL commands.
  • In our example, “‘ OR ‘1’=’1” serves as a simplified SQL injection payload. Let’s break down what this payload does: ‘ OR ‘1’=’1: This payload is crafted to manipulate a SQL query’s logic. In SQL, ‘1’=’1′ is a condition that always evaluates to true. By appending ‘ OR ‘1’=’1 to a query, an attacker can potentially bypass authentication checks or retrieve unauthorized data because the condition ‘1’=’1′ is always true. 

Why Use This Example?

  • In our testing scenario, we’re using “‘ OR ‘1’=’1” as a demonstration to test an API endpoint (https://reqres.in/api/comments) for SQL injection vulnerabilities. By sending this payload as part of the username field in a POST request and checking the response for an error (responseBody.error), we simulate a scenario where the application might mishandle or directly execute SQL commands based on user input. 

Create a test script for SQL Injection in `src/sqlInjection.ts`


Example: Testing for XSS

Understanding XSS Payloads

  • One critical aspect of web application security is understanding and mitigating XSS (Cross-Site Scripting) vulnerabilities. XSS occurs when an attacker injects malicious scripts into web pages that are viewed by other users. These scripts can execute arbitrary code in the context of a user’s session, leading to potential data theft, session hijacking, or other forms of malicious activities.  
  • An XSS payload is the actual malicious script that an attacker attempts to inject into a vulnerable web application. In our example, “<script>alert(‘XSS’);</script>”, we see a typical XSS payload encapsulated within <script> tags. Let’s break down what this payload does: 
    • <script>: This HTML tag is used to define client-side JavaScript within an HTML document. 
    • alert(‘XSS’);: Inside the <script> tags, alert(‘XSS’); is a simple JavaScript function that displays an alert box with the message “XSS”. This is a benign example used for testing purposes, but real-world XSS payloads can be much more malicious, aiming to steal cookies, redirect users, or perform actions on behalf of the victim. 

Why Use This Example? 

In our testing scenario, we’re using “<script>alert(‘XSS’);</script>” as a harmless payload to check if an API endpoint might be vulnerable to XSS attacks. By sending this payload in a POST request to the API endpoint and then checking if it gets reflected back in the response, we can identify potential security weaknesses. 

Create a test script for XSS Injection in `src/xssInjection.ts`: 


Playwright & TypeScript 

Example: Testing for CSRF

Understanding CSRF Tokens 

In web security, Cross-Site Request Forgery (CSRF) is a type of attack where an unauthorized command is executed on behalf of a user who is authenticated. To mitigate CSRF attacks, web applications often use CSRF tokens—a unique token generated per session or request—that are included in requests to validate the origin and authenticity of the request. 

In our example, ‘malicious-token’ is used as a placeholder for a CSRF token. A CSRF token is typically a unique identifier generated by the server and embedded in forms or API requests. Its purpose is to ensure that the request comes from a legitimate user session and not from an attacker’s site. 

Why Use This Example? 

In our testing scenario, we’re using ‘malicious-token’ as a simulated CSRF token to test an API endpoint (https://reqres.in/api/comments). By including this token (‘CSRF-Token’: ‘malicious-token’) in our POST request headers and expecting an error in the response (responseBody.error), we simulate a scenario where the CSRF token is not properly validated or used, potentially indicating a CSRF vulnerability. 

Create a test script for CSRF Injection in `src/csrfInjection.ts`: 

Playwright & TypeScript 


Playwright & TypeScript 


Securing APIs is critical to protect your application and user data. Automated testing with Playwright & TypeScript provides a robust and efficient way to ensure your APIs are secure against common vulnerabilities. By integrating these tests into your CI/CD pipeline, you can continuously validate your APIs, reducing the risk of security breaches. 

In this blog, we explored the importance of API security, common vulnerabilities, and how to set up and run automated security tests using Playwright & TypeScript. Implement these practices to enhance your API security and maintain a resilient application infrastructure.