What is XSS (Cross-Site Scripting)?
Cross-Site Scripting (XSS) is a prevalent security vulnerability found in web applications. It occurs when an attacker successfully injects malicious scripts into content that is served to users. This can happen when an application accepts untrusted data and sends it to a web browser without proper validation or escaping.
Types of XSS
- Stored XSS: In this type, the malicious script is permanently stored on the target server (e.g., in a database) and is served to users who access the affected page.
- Reflected XSS: Here, the injected script is reflected off a web server, often via URL parameters or form submissions. The script is executed immediately upon request.
- DOM-based XSS: This occurs when the client-side scripts manipulate the DOM in a way that allows the injection and execution of malicious code.
Impact of XSS
XSS can lead to a variety of harmful outcomes, including data theft (e.g., session cookies), account compromise, and defacement of web pages. It can also facilitate other types of attacks.
Prevention
To mitigate XSS risks, developers should validate and sanitize all input, use Content Security Policy (CSP), and escape outputs. Adopting secure coding practices and regular security audits can significantly reduce XSS vulnerabilities in web applications.