Description: XSS (Cross-Site Scripting) is a security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. This technique relies on executing JavaScript code in the victim’s browser, which can lead to the theft of sensitive information such as session cookies, user credentials, or personal data. XSS attacks can be classified into three main types: reflected, stored, and DOM-based. In a reflected attack, the malicious script is sent to the server and reflected in the response, while in a stored attack, the script is saved on the server and executed every time a user accesses the affected page. On the other hand, DOM-based attacks manipulate the Document Object Model (DOM) of the browser to execute the malicious code. Preventing XSS involves implementing security measures such as input validation and sanitization, using Content Security Policy (CSP), and properly encoding data before displaying it in the browser. The increasing reliance on web applications and user interaction with dynamic content has made protection against XSS a priority in secure software development.
History: The XSS vulnerability was first identified in the late 1990s when browsers began allowing script execution on web pages. In 1999, the term ‘Cross-Site Scripting’ was coined by security researcher Jeremiah Grossman. As the web evolved, so did the attack techniques, leading to the creation of standards and best practices to mitigate these risks. In 2000, the first recommendations for preventing XSS were published, and since then, the security community has continuously worked to develop tools and techniques to help developers secure their applications.
Uses: XSS is primarily used to steal sensitive information from users, such as login credentials, credit card data, and other personal information. It can also be used to conduct phishing attacks, redirect users to malicious sites, or even propagate malware. In the field of cybersecurity, it is employed to conduct penetration testing and security audits, helping to identify vulnerabilities in web applications.
Examples: An example of a reflected XSS attack could be a search form on a website that does not properly validate user input. If an attacker sends a link that includes a malicious script in the search query, the script will execute in the victim’s browser when they click the link. A case of stored XSS could occur on an online forum where a malicious user posts a comment containing a script. Every time other users visit the comment page, the script executes in their browsers. Lastly, a DOM-based attack could involve manipulating a web application that uses JavaScript to load dynamic content without proper validation.
