Cross-Site Scripting (XSS): How it Works, Types of Attacks, and Steps to Prevent It
“Cross-site scripting (also known as XSS) is a web security vulnerability that allows an attacker to compromise the interactions that users have with a vulnerable application.”
In the ever-growing digital era, threats to web security are becoming increasingly complex, with one of the most frequently encountered threats being Cross-Site Scripting (XSS). In this article, we will explore the concept of XSS, understand how it works, explore the different types of XSS attacks, and most importantly, identify important steps to prevent them. Let's dive into the world of XSS to strengthen our web security defenses.
What is XSS?
Cross-site scripting, better known as XSS, is a gap in website security that allows perpetrators to infiltrate the interactions of a user who is using a website with minimal security. The main purpose of using XSS is to retrieve important data, retrieve cookies from users, or send a script that can damage the user but as if the cause is from the web itself. Therefore, this XSS is not known directly to the website owner himself, which in the end will give a bad impression to the developer regarding his performance in creating the website.
How does XSS work?
how XSS works
After we understand the meaning of XSS, we need to pay attention to how it works and how dangerous this attack is for website developers. Generally, this attack is carried out using Javascript, VBScript, ActiveX, Flash, and other client-side languages. One of them is that the perpetrator will send a link containing a malicious script which is then accessed by the target. After running the target script, the perpetrator will easily get the important data needed. This script can be inserted in various ways, such as through a form or something similar, and then the user will open the page.
Cross-Site Scripting attack type
- Reflected Cross-Site Scripting
This type will appear when the application receives data in the form of an HTTP request that includes a malicious script.
Reflected Cross-Site Scripting
This attack was carried out by the perpetrator by sending a malicious link via email or other social media. When the target clicks on the link, the script can perform any action and retrieve important data that can be accessed. - Stored Cross-Site Scripting
This type is the most destructive because the script will be stored permanently on the target server.
Stored Cross-Site Scripting
The process of this type of attack starts with the perpetrator creating a malicious script in a command input and then uploading it. The victim accesses the website which will then display a malicious script in the response. The victim's browser starts executing the script and sending cookies to the perpetrator's server. - DOM Cross-Site Scripting
The perpetrator does this by entering a script that changes the DOM environment so that the page being accessed looks fine in terms of response, but there is a script that is running which will then be sent to the perpetrator's server.
DOM Cross-Site Scripting
How to prevent Cross-Site Scripting attacks
How to prevent Cross-Site Scripting attacks
- Filter input on arrival
This is done by strictly filtering input received from users. - Encode data on output
This is done when the response from a fire needs to be encoded so that it is not easy for the perpetrator to get important data. - Use appropriate response headers
To prevent XSS in HTTP responses such as Javascript or HTML, we can use the Content-Type and X-Content-Type-Options headers to ensure the browser interprets the response as desired. - Content Security Policy
As a last resort, CSP can be used to reduce the risk of XSS attacks. This feature aims to improve the security of a website which helps detect and reduce certain types of attacks, such as Cross-Site Scripting (XSS), data injection attacks, data theft, site destruction, and distribution of malware.
For most modern frameworks that have been distributed to date, fortunately, they only have a few bugs related to this XSS. However, developers need to pay attention again, several gaps can occur if we use certain frameworks, for example:
- Escape hatch is a framework used to manipulate the DOM directly.
- React's dangerouslySetInnerHTML without using sanitize HTML.
- React cannot handle JavaScript, data, or URLs without special validation.
- Template Injection
- Outdated plugins or framework components
With a deep understanding of the dangers of Cross-Site Scripting (XSS) and effective steps to prevent it, we can strengthen system defenses and protect users from ever-evolving cyber threats. Through awareness and proactive action, we can maintain the security and integrity of websites and move forward towards a safer and more secure internet ecosystem for all users. For other interesting information about technology and IT, visit Radya Blog.
Source:
Cross Site Scripting (XSS) | OWASP Foundation
Cross Site Scripting Prevention - OWASP Cheat Sheet Series
What is cross-site scripting (XSS) and how to prevent it? | Web Security Academy
XSS Explained with React and Vanilla JS Examples | Cross Site Scripting | dangerouslySetInnerHTML
Latest cross-site scripting news | The Daily Swig