Web Security for Front-End Developers: XSS, CSRF, and CORS



Security is no longer just a backend concern. With the growing complexity of front-end applications, every front-end developer must understand key security vulnerabilities and how to safeguard against them. Let's explore three critical areas: Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), and Cross-Origin Resource Sharing (CORS).

1. Cross-Site Scripting (XSS)

What it is: XSS occurs when malicious scripts are injected into web pages viewed by other users. This allows attackers to execute arbitrary code in the browser, steal cookies, or hijack sessions.

Types of XSS:

  • Stored XSS
  • Reflected XSS
  • DOM-based XSS

Mitigation:

  • Escape user input before rendering it in the DOM.
  • Use frameworks/libraries that auto-escape (e.g., React, Angular).
  • Sanitize inputs on both client and server side.
// Avoid
element.innerHTML = userInput;

// Safe
element.textContent = userInput;

2. Cross-Site Request Forgery (CSRF)

What it is: CSRF tricks an authenticated user into submitting a request they didn’t intend, allowing attackers to perform actions on their behalf.

Mitigation:

  • Use anti-CSRF tokens.
  • Verify the Origin and Referer headers.
  • Avoid relying solely on cookies for authentication.
<!-- CSRF token example -->
<input type="hidden" name="csrf_token" value="random_token_value">

3. Cross-Origin Resource Sharing (CORS)

What it is: CORS is a browser mechanism that restricts cross-origin HTTP requests initiated from scripts. It's used to control access to resources outside the current domain.

How to Configure (on server):

Access-Control-Allow-Origin: https://trustedsite.com
Access-Control-Allow-Methods: GET, POST
Access-Control-Allow-Headers: Content-Type, Authorization

Common mistake: Allowing * for Access-Control-Allow-Origin while sending credentials is a security risk.

Conclusion

Security is layered and shared — front-end developers play a crucial role. By understanding XSS, CSRF, and CORS, you can build interfaces that are both user-friendly and secure.

Question for You: What security best practices do you follow in your front-end projects? Share your thoughts or experiences in the comments.

#WebSecurity #FrontendDevelopment #XSS #CSRF #CORS #JavaScriptSecurity #WebDev #SecureCode #WebDevelopment #FrontendTips

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