Common JavaScript Code Vulnerable to XSS Attacks

Image by https://www.offsec.com/app/uploads/2022/04/1920-x-628-XSS.png

JavaScript is an essential part of modern web development, but it also opens the door to vulnerabilities like cross-site scripting (XSS).

XSS attacks occur when malicious scripts are injected into web applications, allowing attackers to steal data, hijack user sessions, or even take control of the entire site.

Unfortunately, many JavaScript developers unknowingly introduce XSS vulnerabilities into their code. Understanding these common pitfalls can help you write more secure applications.

One of the most frequent XSS vulnerabilities happens when developers directly insert user input into the DOM without proper sanitization. Consider the following example:

const userInput = "<script>alert('Hacked!')</script>";
document.body.innerHTML = `Hello, ${userInput}`;

This simple mistake allows an attacker to inject harmful scripts that will execute in the browser. When a user visits the page, the script runs, potentially stealing cookies or redirecting them to a malicious site.

Another common mistake is failing to escape dynamic content when updating elements using innerHTML:

document.getElementById("output…