Cross-Site Scripting (XSS)

Definition & Meaning:

Cross-Site Scripting (XSS) is a type of security vulnerability found in web applications.

It allows attackers to inject malicious scripts into content viewed by other users, potentially leading to unauthorized access to user data, session hijacking, and other malicious activities.

XSS attacks exploit the trust a user has for a particular site, making the user’s browser execute the injected script as if it’s a part of the website.

There are three main types of XSS vulnerabilities: stored, reflected, and DOM-based. Stored XSS occurs when a malicious script is directly stored on the target server, such as in a database, and then presented to users within a web page.

For example, an attacker might post a comment on a blog that contains a script, and any user reading the comment would execute the script.

Reflected XSS happens when a malicious script is reflected off a web application to the user’s browser, often through a link that appears trustworthy.

To protect against XSS attacks, developers use a variety of security measures.

These include sanitizing user input by filtering out or escaping characters that could be used in a malicious script, implementing Content Security Policy (CSP) headers to restrict the sources from which scripts can be loaded, and using secure coding practices to validate or encode user inputs.

For instance, if you run an online forum, ensuring that user-submitted content, like posts or comments, is properly sanitized can prevent attackers from embedding harmful scripts that other users might unwittingly execute.

This involves stripping out or encoding HTML tags and JavaScript before displaying content back to users.