CompTIA Security+: Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS) is a type of security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. XSS attacks occur when an application receives data in an untrusted manner, mostly in web applications with a weak input validation.

Why is it important?

Understanding XSS is essential for security professionals as it can lead to various security issues such as stolen user data, manipulation of web content, and phishing scams. It is a widespread and constantly evolving threat.

What is Cross-Site Scripting?

In a Cross-Site Scripting (XSS) attack, an attacker uses a web application as a conduit to send malicious scripts to a victim's browser. Stored XSS and Reflected XSS are the two most common types.

How does Cross-Site Scripting Work?

Both types of XSS attacks involve an attacker inputting malicious code into a website's Javascript, HTML, or URL. If the user's browser executes the script, the attacker can hijack the user's session, redirect the user to a malicious site, or even rewrite the HTML of the web page.

Exam Tips: Answering Questions on Cross-Site Scripting (XSS)

When preparing for an exam that includes XSS, highlight the characteristics of XSS attacks and note the differences between Stored and Reflected XSS. Remember to focus on prevention measures like input validation, output encoding, and implementing proper security controls.
For questions involving troubleshooting XSS attacks, concentrate on identifying indicators of XSS attacks (such as unexpected behavior in a web application or unusual logs) and appropriate countermeasures. Questions might also cover policy-based XSS prevention, so be sure to understand security policies that can help mitigate XSS attacks.