Table of contents

Introduction

What Is Cross Site Scripting?

2.1.

Example

How does cross-site scripting work?

Types of Cross-Site Scripting

Impact of Cross-Site Scripting

Preventing Cross-Site Scripting

Frequently Asked Questions

7.1.

What is cross-site scripting?

7.2.

Is cross site scripting XSS or CSS?

7.3.

What is the difference between XSS and cross-site scripting?

7.4.

What hacker can do with cross-site scripting?

Conclusion

Last Updated: Aug 13, 2025

Medium

Cross Site Scripting (XSS)

Author Sanjana kumari

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Introduction

Cross Site scripting (XSS) is an attack where an attacker injects malicious executable scripts into the code of a trusted website or app. Attackers often initiate an XSS attack by sending a malicious link to a user and tempt the user to click it.

This article aims to provide a comprehensive understanding of XSS, its different types, impacts, and preventive measures.

What Is Cross Site Scripting?

Cross-Site Scripting operates on the principle of manipulating websites to execute malicious scripts to perform undesirable actions. The peril lies in the fact that these scripts appear to be part of the website itself. Here's a simplistic example of how XSS might occur:

Example

<script>
  // Assume this input is coming from a user
  var userInput = "<script>alert('Hacked!');</script>";
  document.write(userInput);
</script>

In this case, an attacker has managed to inject a script that displays an alert with the message 'Hacked!'.

Also see, Traceability Matrix

How does cross-site scripting work?

Cross-Site Scripting (XSS) is a type of security vulnerability that occurs when a web application allows an attacker to inject malicious scripts into web pages that are viewed by other users. This can happen when the application does not properly validate, sanitize, or escape user input before including it in the output that is sent to the browser.

There are several types of XSS attacks, but they generally involve injecting malicious scripts into web pages that are later viewed by other users. Here's a brief overview of the common types of XSS attacks:

Stored XSS (Persistent XSS): In this type of attack, the malicious script is permanently stored on the target server, such as in a database. When a user visits the affected page, the script is served to their browser along with the legitimate content.
Reflected XSS (Non-Persistent XSS): In this scenario, the injected script is reflected off a web server, but it doesn't persist. The attacker usually tricks the victim into clicking on a specially crafted link containing the malicious payload. The server includes the payload in the response, and the victim's browser executes it.
DOM-based XSS: This type of XSS occurs when the client-side script manipulates the Document Object Model (DOM) of a web page. The attack targets the manipulation of the DOM rather than the server's response. The malicious code can modify the page structure and content dynamically.

Types of Cross-Site Scripting

Let's explore the types of cross-site scripting:

Stored XSS: Here, the malicious script injected by the attacker is permanently stored on the target server.
Reflected XSS: The malicious script is embedded in a URL which is then sent to the victim.
DOM-Based XSS: The vulnerability exists in the DOM (Document Object Model) environment, allowing an attacker to manipulate web page elements.

Impact of Cross-Site Scripting

The aftermath of an XSS attack can be severe. It can lead to:

Data Theft: Attackers can steal sensitive data like passwords and credit card details.
Identity Theft: User identities can be stolen, leading to fraudulent activities.
Malware Distribution: Malicious software can be distributed to unsuspecting users.

Preventing Cross-Site Scripting

Preventing XSS requires a combination of secure coding practices and robust security measures like:

Input Validation: Ensure that all input is validated for proper length, type, and value range.
Output Encoding: Encode data when you are outputting it to the browser to prevent malicious data from being executed as code.
Content Security Policy (CSP): Implementing CSP headers can significantly reduce the risk of XSS.

Content-Security-Policy: default-src 'self';

Frequently Asked Questions

What is cross-site scripting?

Cross-Site Scripting (XSS) is a web security vulnerability where attackers inject malicious scripts into web pages viewed by others. Exploiting inadequate input validation, XSS can compromise user data and execute harmful actions within the context of a trusted website.

Is cross site scripting XSS or CSS?

Cross-Site Scripting is commonly abbreviated as XSS, not to be confused with CSS, which stands for Cascading Style Sheets—a language used for web page styling. XSS refers to a security vulnerability involving the injection of malicious scripts into web pages.

What is the difference between XSS and cross-site scripting?

There is no practical difference between "XSS" and "cross-site scripting." Both terms refer to the same security vulnerability where attackers inject malicious scripts into web pages. "XSS" is the abbreviated and commonly used term for this type of exploit.

What hacker can do with cross-site scripting?

With Cross-Site Scripting (XSS), a hacker can execute malicious scripts in users' browsers, leading to various attacks. This includes stealing sensitive information, session hijacking, defacement of websites, distribution of malware, and performing actions on behalf of authenticated users without their consent.

Conclusion

Cross-Site Scripting stands as a formidable threat in the realm of web application security. Understanding its mechanics, impact, and the measures to mitigate it is pivotal for developers and web administrators alike. As the digital world continues to evolve, staying a step ahead in security practices is imperative to safeguarding data and ensuring a safer web experience for all users.

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