What is Cross Site Scripting (XSS)?

What is Cross-Site Scripting (XSS)?

One of the most frequently asked questions by individuals interested in the online world is, "What is Cross-Site Scripting?" or "What is XSS?". Cross-Site Scripting, commonly referred to as “XSS” or “XSS vulnerability,” involves creating various malicious scripts aimed at online sites. It is also used to carry out external attacks on applications with security vulnerabilities. XSS constitutes a code injection attack targeting online applications that send malicious scripts. These harmful scripts caused by Cross-Site Scripting can lead to session hijacking, exposure of sensitive data, and even worse consequences. Instead of targeting the host or the computers themselves, XSS attacks often focus on the users of these applications.

In Cross-Site Scripting, malicious content is manipulated using JavaScript through a vulnerable site, aiming directly at attacking users. If an online application or page uses unfiltered user input to dynamically create HTML code, it becomes vulnerable to Cross-Site Scripting (XSS). If this input contains malicious scripts, it is appended to the page’s code and executed via the browser, leading to various script-based attacks. However, JavaScript is widely used in modern XSS attacks due to its foundational role in many browsing experiences.

How Does Cross-Site Scripting (XSS) Work?

Cross-Site Scripting (XSS) is one of the most common online security issues. To better understand the answer to "What does XSS do?", it’s important to explore how Cross-Site Scripting works.

Many cybercriminals operate in the online world. These cybercriminals first identify a target site. Then, they detect vulnerable functions that accept user input, such as search bars, comment boxes, and login forms.

After identifying these functions, the cybercriminals inject malicious codes into them. These harmful codes are typically written in well-known programming languages such as JavaScript or HTML.

The next step for the cybercriminals is to embed the malicious codes into the online page via the vulnerable function. These codes then become part of the site, creating a dangerous situation.

Depending on how the code is injected, this malicious content may not even appear on the actual site. Instead, it may seem like an existing element of the page, creating a false and temporary impression.

As a result, the site may seem compromised even if it isn’t. Consequently, users may become victims of security breaches by visiting this page due to cybercriminal activity.

This is where the XSS vulnerability comes into play. Given the threats it can cause, online site and application developers or users must pay attention to such security flaws. Regularly implementing the necessary precautions and performing security checks can provide a significant advantage against Cross-Site Scripting (XSS).

How to Prevent Cross-Site Scripting (XSS)?

There are several types of XSS attacks. Persistent, Reflected, and DOM-based XSS attacks are the most common and dangerous types, causing issues for both users and developers. Therefore, the question “How can Cross-Site Scripting (XSS) be prevented?” is asked almost as often as “What is XSS?”.

To ensure the security of online applications and sites, all relevant parties must be aware of the risks associated with security vulnerabilities. Hence, proper training is essential.

• Treat All User Input as Untrusted: Every user input to applications and sites poses a Cross-Site Scripting risk. Therefore, all user inputs should be treated as "untrusted."
• Use Appropriate Encoding: Apply proper encoding methods, such as JavaScript, CSS, HTML, and URL escaping, for user inputs. Developers are advised to use existing libraries rather than custom implementations.
• Filter HTML Codes: The reason user inputs can contain HTML codes is that these inputs have the ability to break valid tags. Such codes do not allow counter-coding. Therefore, developers must use validated and trusted libraries.
• Set the HttpOnly Flag: To minimize XSS vulnerabilities, the "HttpOnly" flag should be set. This flag prevents cybercriminals from accessing defined information through JavaScript.

Implement Content Security Policy (CSP): To further reduce XSS vulnerabilities, developers should use a Content Security Policy (CSP). Acting as an additional security layer, CSP functions as a gatekeeper against attacks.

The Importance of Knowledge in Building a Secure Career in Technology

Given the potential threats posed by XSS vulnerabilities, possessing the right knowledge is crucial for building a secure career in the tech world. If you’re considering a career in this field or looking to take your current career to the next level, visit our "Career Guide" page for guidance.

Additionally, to stay updated on the latest job opportunities in the tech sector, check out our technology job listings page. You can explore open positions at leading companies and take the next step in your career.

Stay secure, and stay connected with technology!