How to Prevent XSS Vulnerability
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How to Prevent XSS Vulnerability

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Cyberattacks are on the rise. They’re also becoming more sophisticated.

In fact, there has been a recent uptick in cross site scripting (XSS) attacks. During summer 2021, 10 Magecart attacks were detected targeting a shopping cart application. Hackers stole payment details for 38,000 users via different e-commerce websites. And with 230.5 million Americans shopping online in 2021, these attacks will only keep becoming more attractive to criminals.

You need to develop an appropriate response by measuring risks and choosing the right solutions. One of the areas to look into is XSS vulnerability testing. Bugs and other issues can leave you at risk for attacks in which a hacker injects malicious code. Here’s what you need to know about XSS or cross site scripting.

An overview of XSS vulnerabilities

Before we discuss XSS attacks further, it’s important to understand a few things about malicious code.

How does code work?

Code is the text in a programming language. Examples include C++, Java, PHP or HTML for webpages.

Humans create this text. However, additional steps must be taken before a machine can use it:

  • Code goes through a compiler. It turns the text into an object file.
  • A program called a linker combines this object file with other preexisting object files if needed.
  • The result is an executable file. This file tells the computer or server what to do.

This process can vary from one language to another. In some instances, an interpreter turns the code directly into an executable file.

Ideally, the compiler knows if code is safe or not. But if an XSS vulnerability is present, the compiler processes the code no matter its origin.

How does code injection work?

A code injection attack sends malicious code to a compiler. There, it becomes an executable file. As a result, the web application does something the user didn’t ask for.

There are different types of code injection attacks. A hacker can, for instance, manipulate SQL queries to access a database. They can also target SSL protocols to steal encryption keys. Cross site scripting is another type of code injection attack.

What is cross site scripting?

Cross site scripting attacks use input fields to send harmful code to a compiler. An input field can be a comment box, a contact form, a forum post or even a URL field.

These attacks often try to change the behavior of a page when a browser-side script runs. A browser-side script is an application that makes a webpage dynamic. A static webpage always shows the same content, but a dynamic page loads differently depending on what the user wants to do. Examples include using a search box or buying something with a shopping cart.

These scripts can run on either a browser or a server. It’s possible to inject malicious code at both levels. In some cases, the user notices that there is a problem right away. This can happen if a hacker uses this technique to deface a webpage.

XSS vulnerabilities also open the door for attacks that are hard to detect. For example, hackers can:

  • Steal a user’s login credentials.
  • Perform an action in place of the user.
  • Take over a user’s account.
  • Use malicious code to modify a link. This link will redirect people to a page that downloads malware.
  • Steal sensitive data. This data can include payment or personal information like medical records.

Are XSS attacks common?

We highly recommend adding XSS vulnerability testing to your current cybersecurity plan. Cyberattacks are on the rise as a whole. On average, hackers attack 30,000 websites each day.

We’re also seeing more attacks with a financial motive. It’s true that XSS attacks are more sophisticated than other schemes. They require skill. However, because these attacks can result in financial gains, you should assume that risks are high.

It’s also important to know that XSS vulnerabilities are common. Someone can inject code at different levels. And, as web applications become more complex, there are more ways of injecting code.

Understanding different types of cross site scripting vulnerabilities

Criminals can inject code at different levels. Understanding the different types of vulnerabilities that exist will help you build a strong XSS vulnerability testing strategy.

Stored XSS

In a stored XSS attack, a hacker injects code on a server and it remains there. Every time a user requests a webpage, the server runs the malicious code.

Attackers can inject code via a database, a comment or a forum post. They can also target back-end applications. This technique is known as blind cross-site scripting. A hacker can, for instance, include a piece of malicious code when sending a contact form. The code will run when a customer service representative opens the form.

Reflected XSS

Reflected attacks also happen at the server level, but the code isn’t on the server. Instead, the user injects the code and gets a malicious response reflected back to them.

Most users won’t send malicious code to a server on purpose. However, it’s possible to trick users into clicking a malicious link. These URLs contain malicious code as part of their path. The URL takes users to a real site, where they get a modified version of the page with the malicious script.

DOM-based XSS

DOM-based XSS attacks don’t target servers directly. Most web browsers use a DOM, or Document Object Model, environment. It’s a programming interface that represents the different elements of a webpage. It also helps the browser load the page properly.

Hackers can inject malicious code into the DOM. They often send a modified URL to the victim to do it. Then, when the browser loads the page, it also executes the code.

Access XSS vulnerability testing now

An XSS attack can have serious effects. Vulnerability testing should be a priority given how common these vulnerabilities are.

You can take steps to protect yourself. A managed service provider, or MSP, can help you find problems and implement XSS vulnerability testing.

SecureTech is an MSP based in San Antonio, TX. Cybersecurity is one of our areas of expertise, and we can help you adopt the right solutions to prevent XSS attacks. Get in touch with us to learn more about how we can help!