What is Cross-Site Scripting (XSS) With Examples For Beginners?

Introduction

These days, it’s far more accurate to think of websites as online applications that execute a number of functions, rather than the static pages of old. Much of this robust functionality is due to widespread use of the JavaScript programming language. While JavaScript does allow websites to do some pretty cool stuff, it also presents new and unique vulnerabilities — with cross-site scripting (XSS) being one of the most significant threats.

What is Cross-Site Scripting (XSS)?

Cross-site scripting, commonly referred to as XSS, occurs when hackers execute malicious JavaScript within a victim’s browser.

Unlike Remote Code Execution (RCE) attacks, the code is run within a user’s browser. Upon initial injection, the site typically isn’t fully controlled by the attacker. Instead, the bad actor attaches their malicious code on top of a legitimate website, essentially tricking browsers into executing their malware whenever the site is loaded.
The Use of JavaScript in Cross-Site Scripting

The use of JavaScript in Cross-Site Scripting (XSS) attacks is a significant security threat because JavaScript is a powerful scripting language that is commonly used on the web. The following are some of the key points and examples of how JavaScript can be used in XSS attacks:

1. Stealing Sensitive Information: Attackers can use JavaScript to steal sensitive information, such as login credentials, from unsuspecting victims. For example, an attacker can inject a malicious JavaScript code into a web page that captures the user's login credentials and sends them to the attacker's server.

1. Altering the Appearance of a Web Page: Attackers can use JavaScript to alter the appearance of a web page and present false information to victims. For example, an attacker can inject a malicious JavaScript code into a web page that changes the displayed text or images to something misleading or harmful.

1. Redirecting Victims to a Malicious Site: Attackers can use JavaScript to redirect victims to a malicious site, where they can be tricked into downloading malware or revealing sensitive information. For example, an attacker can inject a malicious JavaScript code into a web page that redirects the victim to a fake login page where the attacker can capture the user's login credentials.

These are just a few examples of how JavaScript can be used in XSS attacks. It is important for web developers to understand the risks associated with using JavaScript and to implement appropriate mitigation techniques, such as input validation, encoding, escaping, and strict mode, to prevent XSS attacks.

How Do Cross-Site Scripting Attacks Work?

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