Cross Site Scripting (XSS) Attack

What is Cross Site Scripting (XSS) ?

Cross-Site Scripting (XSS) attack is a type of web-based attack that involves an attacker injecting malicious code into a web page viewed by other users. This allows the attacker to steal user data, hijack user sessions, or take control of the affected user's browser.

How it Works ?

Cross-Site Scripting is typically done through input fields or parameters that allow user-generated content, such as comments or search queries. An attacker can inject code, such as JavaScript, into the web page and when other users view that page, the code is executed in their browser.

XSS attacks can be launched using a variety of techniques, including social engineering, cross-site request forgery (CSRF), and clickjacking. Social engineering involves tricking users into clicking on a link or visiting a website that contains the malicious code. CSRF involves exploiting a vulnerability in a website to force a user to perform an action without their knowledge or consent. Clickjacking involves tricking a user into clicking on a hidden or disguised button or link.

Types of XSS Attacks:

There are several types of XSS attacks, including:

1. Reflected XSS

In this type of attack, the malicious code is injected into a parameter or input field that is immediately reflected back to the user. For example, the attacker might create a URL with the malicious code and send it to the victim. When the victim clicks the link, the code is executed in their browser.

2. Stored XSS

In a stored XSS attack, the attacker injects the malicious code into a database or other storage location, where it is then retrieved and displayed to other users. For example, the attacker might post a comment on a website that contains the malicious code. When other users view the comment, the code is executed in their browser.

3. DOM-based XSS

In this type of attack, the malicious code is injected into the Document Object Model (DOM) of the web page. This can occur when the website uses JavaScript to process user input without properly sanitizing it.


To prevent XSS attacks, web developers can implement the following measures:

  • Input Validation:
    Validate all user input and sanitize it to remove any malicious code.

  • Output Encoding:
    Encode all output to prevent any malicious code from being executed.

  • Content Security Policy (CSP):
    Implement a CSP that specifies which domains can execute JavaScript on the website.

  • Use Security Frameworks and Libraries:
    Use security frameworks and libraries that provide protection against XSS vulnerabilities.

Users can also protect themselves by using browser extensions that block scripts or by disabling JavaScript in their browsers. Additionally, users should be cautious when clicking on links or visiting websites that they are not familiar with.

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