What Are Three Types of Cross Site Scripting?


Scott Campbell

When it comes to web application security, one of the most common vulnerabilities that developers need to be aware of is Cross Site Scripting (XSS). XSS occurs when an attacker is able to inject malicious scripts into a trusted website, which are then executed by unsuspecting users. This can lead to various consequences, such as theft of sensitive information or the compromise of user accounts.

Types of XSS:

1. Stored XSS:

Stored XSS, also known as persistent or type I XSS, is a type of attack where the malicious script is permanently stored on a Targeted website’s server.

The injected script is then served to users whenever they access specific pages or view particular content. This makes stored XSS particularly dangerous as it can affect multiple users over an extended period of time.


Imagine a social media website that allows users to post comments on other people’s profiles. If an attacker figures out how to inject a malicious script into a comment field and it gets stored on the server, every time someone views that profile page, the script will execute in their browsers.

2. Reflected XSS:

Reflected XSS, also known as non-persistent or type II XSS, occurs when the injected script is embedded within a URL and only affects users who click on that specific link. Unlike stored XSS, the injected code is not permanently stored on the Targeted server but rather reflected back in the response from the server.


An attacker could craft a malicious URL containing a script that prompts users for their login credentials on a legitimate-looking login page. If victims click on this URL and enter their credentials, they unknowingly provide them directly to the attacker.

3. DOM-based XSS:

DOM-based XSS, also known as type 0 XSS, is a variant of XSS where the vulnerability arises from the insecure handling of data by JavaScript on the client-side. In this scenario, the malicious script is not sent to the server but rather directly manipulated by JavaScript in the browser’s Document Object Model (DOM).


Let’s say a website uses JavaScript to dynamically update its content based on user input. If an attacker is able to inject a script that alters this dynamic content in a malicious way, such as redirecting users to a phishing page, then any user who interacts with that manipulated content will be affected.


Cross Site Scripting (XSS) is a serious security vulnerability that can have severe consequences for websites and their users. It is important for developers to understand the different types of XSS attacks, such as stored XSS, reflected XSS, and DOM-based XSS, in order to implement proper security measures and protect against these threats.

  • Stored XSS: A permanent injection of malicious scripts that affect multiple users over an extended period of time.
  • Reflected XSS: An injection of scripts embedded within URLs that only affects users who click on specific links.
  • DOM-based XSS: A variant where the vulnerability arises from insecure handling of data by JavaScript on the client-side.

By understanding these types of XSS attacks and taking appropriate precautions during web development, we can help ensure the safety and security of both our websites and their users.

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