JavaScript and Security Explained

Key Concepts

Understanding JavaScript security involves several key concepts:

• Cross-Site Scripting (XSS)
• Cross-Site Request Forgery (CSRF)
• SQL Injection
• Content Security Policy (CSP)
• Secure Data Handling
• Input Validation and Sanitization

Cross-Site Scripting (XSS)

XSS is a vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. This can lead to data theft, session hijacking, and other malicious activities.

// Example of XSS vulnerability
<div>
    <script>alert('XSS Attack!');</script>
</div>
    

Imagine XSS as a malicious note slipped into a public bulletin board. When others read the board, they inadvertently execute the note's instructions.

Cross-Site Request Forgery (CSRF)

CSRF is an attack that tricks the victim into submitting a malicious request. It exploits the trust a website has in the user's browser.

// Example of CSRF attack
<img src="http://bank.com/transfer?amount=1000&to=attacker" />
    

Think of CSRF as a forged letter, signed with your signature, instructing your bank to transfer money without your knowledge.

SQL Injection

SQL Injection is a technique where an attacker can execute arbitrary SQL code on a database, leading to data leakage, modification, or deletion.

// Example of SQL Injection vulnerability
let userId = req.query.userId;
let query = SELECT * FROM users WHERE id = ${userId};
    

Imagine SQL Injection as a backdoor key that allows unauthorized access to a secure vault, bypassing all security measures.

Content Security Policy (CSP)

CSP is a security feature that helps prevent XSS and other code injection attacks by specifying which sources of content are allowed to be loaded.

// Example of CSP header
Content-Security-Policy: default-src 'self'; script-src 'self' https://trusted.com
    

Think of CSP as a bouncer at a club, only allowing in guests who meet specific criteria, thus keeping out unwanted visitors.

Secure Data Handling

Secure data handling involves protecting sensitive information from unauthorized access and ensuring it is encrypted during transmission and storage.

// Example of secure data handling
const bcrypt = require('bcrypt');
const saltRounds = 10;
const myPlaintextPassword = 'userPassword';
bcrypt.hash(myPlaintextPassword, saltRounds, function(err, hash) {
    // Store hash in your password DB.
});
    

Imagine secure data handling as a locked safe, where sensitive documents are kept safe from prying eyes.

Input Validation and Sanitization

Input validation and sanitization ensure that user inputs are safe and do not contain malicious code or unexpected data.

// Example of input validation and sanitization
function sanitizeInput(input) {
    return input.replace(/&/g, '&').replace(//g, '>');
}
    

Think of input validation and sanitization as a filter that removes impurities from water, ensuring it is safe to drink.