Cross Site Scripting

Cross Site Scripting

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Cross-Site Scripting (XSS) is a type of security vulnerability typically found in web applications. XSS enables attackers to inject malicious scripts into web pages viewed by other users. These scripts can then be executed in the victim’s browser, leading to a variety of potential attacks, such as stealing session cookies, defacing websites, or redirecting the user to another site.

XSS attacks can be categorized into three types: Stored, Reflected, and DOM-based.

  1. Stored XSS (Persistent XSS): The malicious script is permanently stored on the target server, such as in a database, in a forum message, in a comment field, or in other user-generated content areas. When a user views the stored data, the attacker’s malicious script is executed.
  2. Reflected XSS (Non-Persistent XSS): The malicious script is embedded in a URL. The server includes the malicious script from the URL in the response, and the script is then executed within the victim’s browser. For this attack to work, the attacker must trick the victim into clicking a specially crafted link (for example, through a phishing email or malicious web ad).
  3. DOM-based XSS: The attack payload is executed as a result of modifying the Document Object Model (DOM) in the victim’s browser used by the original client-side script. This happens when a script uses input to dynamically create a part of the DOM, which then gets executed by the browser.

To protect against XSS attacks, it’s essential to properly validate, sanitize, and escape user input, and not insert untrusted data directly into HTML output. Additionally, modern browsers often include features to mitigate the risk of XSS attacks, such as the SameSite attribute for cookies and Content Security Policy (CSP) headers. Also, web application firewalls can often detect and block XSS attacks.

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