What Is Cross-Site Scripting (XSS)

Cross-Site scripting is a security exploit where an attacker attaches a malicious code onto a legitimate website that executes when the victim visits the website or opens the web application on their device. If code execution is successful, it allows the attacker to bypass security access controls and steal user identities.

It can be challenging to identify XSS vulnerabilities even for IT personnel with basic knowledge in cybersecurity or programming. Once an XSS attack is successful, removing the malicious code from the infected we application is not easy.

Types of XSS Attacks

Attackers can implement Cross-Site Scripting in different ways depending on your web system vulnerabilities. Cross Site Scripting Attacks include but are not limited to:

• Non-persistent (Reflected) attack

The attacker tricks the user into browsing a malicious site, submitting a form, or clicking a link. The injected script and its payload are loaded into the vulnerable website. The web server echoes back the injected script to the user’s browser in the form of a search result, error message, or any other.

• Persistent (Stored) attack

In this attack, the injected script and its payload are stored permanently in the target server’s database and served to other victims when their browser requests data from the server.

• Document Object Model (DOM) Attacks

The malicious script exploits a security vulnerability on the client-side code and runs in the user’s browser instead of the webserver (Server-side code).

Please note that an attacker can deploy a combination of the above methods in a single attack. Other forms of attacks are not very common, such as self-XSS and mutated XSS, among other emerging techniques.

How Does Cross-Site Scripting Work?

XSS attacks are implemented in different ways, as described above. However, most of these attacks follow a similar process:

1. The attacker will identify a website that allows users to add content to the web page. Employ social engineering techniques to lure users to visit that specific website.
2. The identified victim visits the site and probably enters some data. Their device will accept the script and execute it since it is considered part of a trusted website’s source code.
3. Once the script runs, it may access the user’s data or interfere with the webserver.

What are the threats of XSS?

XSS attacks can result in significant adverse effects on users. These threats include:

• The attacker can install the malware on the device

• The attacker can steal your data from cookies and masquerade as the real you

• Successful server-side attacks can result in reputational damage or financial loss

How can you prevent cross-site scripting?

There are several ways you can prevent cross-site scripting, such as:

• Use a template system with auto-escaping that is context-aware

• Limit or prevent users from submitting content via the company website

• Filter all user input on arrival and encode data when displaying results

• Perform thorough penetration testing on your website to ascertain its resilience.

If you suspect that you are a victim of an XSS attack, perform a security review of your web application code and identify any HTTP input request stored in the back-end and then displayed as an HTML output by the web application. This security review can only be done by an expert with experience in web applications and cybersecurity. You may not have such in-house expertise.

Let us help you

At Verified Safe, we know how script-based attacks work and have developed practical solutions to prevent them. We will work with you to identify existing XSS vulnerabilities and patch them immediately to prevent any imminent attacks. We will create a custom solution that suits your security needs. Talk to us today by dialing 615-547-9563 and get the best cybersecurity solutions.