What Is XSS, and How Can I Detect It?

Use a XSS vulnerability scanner such as Netsparker to automatically detect any type of Cross-site scripting vulnerability, including blind and reflective XSS, DOM XSS and persistent XSS.

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Cross-Site Scripting (XSS) is one of the oldest web application vulnerabilities on the threat landscape, but it remains an active risk. Industry studies find that XSS vulnerabilities still abound in production, and it remains part of the OWASP Top Ten list of web application security risks. In order to protect your clients' data, and retain their trust, you need to have a plan to identify and remediate XSS vulnerabilities in your company's web applications.

What Are Cross-Site Scripting Attacks?

There are three major types of XSS. At its heart, all kinds of XSS involve an attacker being able to make a web application execute malicious JavaScript code when users attempt to load the site. That can lead to the compromise of sensitive information.

In stored XSS, an attacker directly submits code to a web application via a user input field, and that script is stored on the web page. It is run whenever a user loads the site in their web browser, with the normal privileges of that website.

Reflected XSS, the most common type according to OWASP, requires a user to click a malicious link. The link contains parameters that contain attacker-created code, which is then "reflected" back to the target in the HTTP response and executed in their web browser.

DOM-based XSS executes completely on the client side. A user clicks a link with JavaScript code in a URL parameter, and if the web application is not instructed to scrub out code injected in parameters, the JavaScript instead renders the contents between the HTML < script > tags when the code that uses the parameter is run.

How Should I Choose an XSS Scanner?

The first step toward fixing the XSS vulnerabilities in your environment is to identify them. In order to do that, you need a vulnerability scanner that can map out and accurately detect XSS no matter what technologies the application is built and hosted on.

Netsparker is platform-independent. Whether a web application is based on a framework like WordPress, Drupal, or Joomla!, or it is custom and unique to your organization, Netsparker scans it reliably. Furthermore, it functions no matter what the underlying technologies are. Whether the server side of the application runs in Python, PHP, Ruby, .NET, Java or any other language, our scanner will map out the web pages on the attack surface and identify all three kinds of XSS vulnerabilities.

Web security scanner results are also only useful if they are actionable. Netsparker's Proof-Based Scanning™ provides proof of exploit for the findings. Not only does the scan report show when XSS vulnerabilities are found, but it shows exactly what code was sent from the scanner to the web application, and exactly what information was compromised as a result. Instead of other security tools that require hours of manual validation, these dead accurate results mean that the IT security team can delegate remediation tasks more quickly, and move on to other vulnerability scanning or penetration testing tasks as necessary.

The result of the scan report can be customized based on the audience. Developers can see detailed proof of exploit for the applications they work on, complete with the HTTP requests and HTTP responses connected to the XSS attacks. That way, they can hone in on the vulnerable code sooner, and craft fixes more quickly. The IT Security team can also provide an executive-level report for management. Management can see the trends in web application vulnerabilities over time, and make educated decisions about where to focus the security budget.

See Netsparker For Yourself

See for yourself how Netsparker can help you find XSS vulnerabilities and keep sensitive data secure. Netsparker Web Application Security Scanner comes in two editions, both a cloud version and a Microsoft Windows desktop version. Sign up for your free demo of Netsparker today, and learn why so many top businesses trust us as their foundation for securing their web applications.

What our customers are saying

"I had the opportunity to compare external expertise reports with Netsparker ones. Netsparker was better, finding more breaches. It’s a very good product for me."
"As opposed to other web application scanners, Netsparker is very easy to use. An out of the box installation can detect more vulnerabilities than any other scanner."
"We chose Netsparker because it is more tailored to web application security and has features that allow the university to augment its web application security needs."