I'm trying to understand Cross-site scripting (XSS). Please explain what XSS is, how it works, and list three key methods for preventing XSS attacks, according to the PortSwigger Web Security Academy.
Navigate to 'https://portswigger.net'. Click on the 'Academy' link in the main navigation. On the 'Web Security Academy' page, scroll down to the 'Client-side topics' section. Click on the 'Cross-site scripting (XSS)' link. Locate and extract the definition of Cross-site scripting (XSS) from the 'What is cross-site scripting (XSS)?' section. Locate and extract an explanation of how XSS works from the 'How does XSS work?' section. Navigate to the 'Preventing XSS attacks' section (either by scrolling or using the table of contents if available). Identify and list three distinct methods for preventing XSS attacks. Synthesize all gathered information into a comprehensive answer.
The agent successfully navigates to the 'What is cross-site scripting (XSS) and how to prevent it?' page. The agent states that XSS is a web security vulnerability allowing an attacker to compromise user interactions with a vulnerable application, circumvent the same origin policy, masquerade as a victim user, and potentially gain full control over application functionality and data. The agent explains that XSS works by manipulating a vulnerable website to return malicious JavaScript to users, which executes in the victim's browser, compromising their interaction with the application. The agent lists three distinct methods for preventing XSS attacks, such as 'HTML-encoding untrusted data', 'URL-encoding untrusted data', 'validating untrusted input', 'using a Content Security Policy (CSP)', or 'sanitizing HTML input'.