In the world of websites, scripts play an essential role in defining the behaviours of websites and web applications. Although scripts are invisible to viewers, they handle things such as the video player on YouTube, what happens when you click the hamburger icon, what happens when you enter your contact information or credit card information, and what happens when you log in to a website. Scripts are an integral part of our daily internet usage.

According to the Open Web Application Security Project (OWASP), Cross-Site Scripting, also known as XSS, is a type of security vulnerability commonly found in web applications. XSS attacks enable attackers to inject malicious scripts into web pages viewed by other users. This type of cyber-attack occurs when a hacker uses input fields such as a search bar, contact information fields, file upload functionalities, etc. to input their own malicious commands or scripts. XSS is a code-injection attack that has existed since the 1990s and remains one of the OWASP Top 10 vulnerabilities to this day.

Example of XSS

The code below shows basic HTML code:

<div style=”background:url(‘/img/some.image.jpeg’)”>

This code is not malicious and provides a URL path to an image file to be displayed in the background of the “div” element.
However, if an attacker can change the URL path of the image and inject something else, the XSS would look something like this:

<div style=”background:url(‘javascript:alert(1)’)”>

This code is still not inherently malicious, but the behaviour of the website has completely changed. It will now pop up with an alert message saying “1” when the web page is opened instead of displaying a background picture.
With this capability, an attacker can change the behaviour of the website to perform any task that they wish, including monitoring the victim’s actions, geolocating the victim, stealing and taking over the victim’s session, stealing credit card information, and potentially taking over the victim’s system.

Prevention of XSS

Developers can implement protections in their applications to prevent XSS attacks by following these best practices:

• Ensure all variables go through a validation
• Always sanitize user input
• Utilize the framework’s built-in security protections
• Use output encoding
• Use safe sinks when directly placing variables into a webpage
• Use appropriate security headers

For a more detailed approach to protecting against XSS attacks, developers can make use of the OWASP Cross-Site Scripting Prevention Cheat Sheet. This cheat sheet is a list of techniques to prevent or limit the impact of XSS. Remember, no single technique will solve XSS. Using the right combination of defensive techniques is necessary to prevent XSS.

Regular users can also protect themselves from becoming victims of XSS attacks by following the best practices below:

• Only visit trusted websites
• Do not click on untrusted links
• Have malware protection software installed

Now you have an idea of the XSS vulnerability. This is just one of the many vulnerabilities that the Anvaya Solutions team members may discover (if they exist).

Schedule a complimentary cybersecurity consultation with the experts at Anvaya Solutions and learn how Anvaya can start helping your organization enhance your security posture with pro-active cybersecurity.