A full stack web developer is a person who can develop both client and server software.

• Program a Browser (JavaScript, Frameworks, Libraries)
• Program a server (PHP, ASP, Python, Node)
• Program a database (SQL, SQLite, MondoDB)

Cross-Site Scripting (XSS)

XSS is a security vulnerability where an attacker injects malicious scripts into content that users trust, often leading to unauthorized access to sensitive data or hijacking user sessions.

• Stored XSS: The malicious script is stored on the server and executed when the victim loads the page.
• Reflected XSS: The malicious script is reflected off a web server (e.g., in a URL query string) and executed immediately.
• DOM-based XSS: The vulnerability occurs when JavaScript modifies the DOM and executes malicious content.

How to Prevent XSS:

• Sanitize Inputs: Always sanitize user inputs using libraries like DOMPurify.
• Escape Outputs: Use functions to escape special characters when displaying user data in the HTML.
• Use Content-Security-Policy (CSP): Implement CSP to restrict what resources can be loaded and executed.

Cross-Site Request Forgery (CSRF)

CSRF is an attack that tricks a user into executing unwanted actions on a different site where they are authenticated.

How CSRF Works:
1. The attacker sends a request from their site, pretending to be the user.
2. The victim is tricked into sending the request while logged into a target site.
3. The server executes the action on behalf of the attacker without realizing the user’s intention

How to Prevent CSRF:

• Use Anti-CSRF Tokens: These are tokens that are included in each request to verify that the request came from the legitimate site.
• SameSite Cookies: Set the SameSite attribute on cookies to prevent sending cookies on cross-site requests.
• Double-Submit Cookies: Use a combination of cookies and request parameters for verification.

Cross-Origin Resource Sharing (CORS)

CORS is a security feature that allows servers to control how resources on the web are requested from other domains.

CORS Policy:
• Same-Origin Policy (SOP): By default, a web page can only request resources from the same domain, protocol, and port.
• CORS allows web applications to request resources from domains other than the origin.

Password Management and Authentication

• Password Storage: Never store plain text passwords. Always hash passwords using secure algorithms like bcrypt or argon2.
• Secure Authentication:Use OAuth2 or JWT (JSON Web Tokens)for secure authentication mechanisms.
  • JWT allows safe transmission of claims (e.g., user identity) in a token that can be verified on the server.

Secure JavaScript Practices

• General Best Practices: Avoid eval() and setTimeout() with string arguments: These functions can execute arbitrary JavaScript, making the application vulnerable to injection attacks.
• Always Use HTTPS: SSL/TLS Encryption: Ensure your site uses HTTPS to protect data from being intercepted by attackers.
  • Always redirect HTTP to HTTPS using server-side redirection.