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XSS Attacks: What They Are, How They Work, and How to Prevent Them

XSS Attacks: What They Are, How They Work, and How to Prevent Them

The internet plays a pivotal role in daily life, such as to correspond with coworkers, check our bank balances, and reserve flights and hotel rooms for upcoming business trips. However, hackers and other malicious actors lurk across the dark web, lying in wait to steal your most sensitive information. If this information is lost or stolen, the consequences can be dire. Consider that the average data breach worldwide costs $4.35 million and takes 277 days – more than nine months – to contain, according to IBM¹. Therefore, you must keep a watchful eye on any suspicious activity on your business’s website and web applications. 

One such activity is cross-site scripting (XSS). XSS attacks inject malicious code into vulnerable web applications so that attackers can steal the valuable information therein². XSS does not target your applications directly, but rather those who use them, because if these attacks are successful, your business’s reputation will collapse². If your reputation is tarnished, customers will then distrust and even abandon you in favor of competitors². Now, you may ask yourself, “How can I keep my business’s networks safe from XSS attacks?” 

Fortunately, there are some best practices you can follow to stop XSS attacks in their tracks or prevent them entirely. In this article, we will learn more about how XSS attacks work and how you can keep them from wreaking havoc on your business. 

XSS occurs when attackers manipulate vulnerable websites to return malicious scripts to users². While this process involves JavaScript, XSS attackers can use programming environments like ActiveX, Flash, and VBScript². Since XSS attacks can occur on multiple client-facing platforms, they are a major threat to your business². Consider British Airways, for example. In 2018, the UK’s flagship airline was attacked by high-profile hacking group Magecard, who exploited an XSS vulnerability in Feedify, a JavaScript library used on British Airways’ website². The attackers modified the script, sending customer data to a malicious website with a similar domain name to the real British Airways². They also included an SSL certificate to trick users into falsely believing they were purchasing tickets from a secure site². While the hackers’ efforts were eventually thwarted, they still skimmed credit card information from 380,000 online booking transactions². This shows the harm that XSS attacks can cause to your company. 

You must also keep in mind that XSS attackers use a variety of methods to infiltrate your company’s websites and web applications². For instance, they may target functions on your website that accept user inputs, including comment boxes, login forms, and search bars². Attackers load their malicious code on top of your legitimate website, thus deceiving your browser into running their malware whenever you load the site². They may also run JavaScript on victims’ browser pages, providing an avenue for them to steal valuable business and personal information during each session². Consider, too, that XSS attackers often impersonate users to compromise their private accounts². Now that you know how XSS attacks work, we will explain best practices for preventing them. 

One best practice for preventing XSS attacks is to ensure all your business’s software applications are up to date³. Updating your software regularly not only lets you install new features and enhance overall performance, but it also keeps attackers at bay by fixing bugs and patching any security vulnerabilities you may have³. Therefore, by preventing your software from becoming painfully outdated, you can easily thwart XSS attackers from infiltrating your company’s websites and web applications, saving you plenty of headaches and sleepless nights³. 

While updating your business’s software is crucial, you must not overlook the importance of application auditing, either³. You should perform regular audits of all your business applications to determine which ones you use most and least often³. If there are any apps you use infrequently, you must delete them to reduce your vulnerability to harmful XSS attacks³. Any way you slice it, updating and auditing your software gives you peace of mind so you can focus on delivering predictably awesome web experiences for everyone in your organization. 

Another best practice for preventing XSS attacks is to sanitize and validate input fields on your company’s website and web applications³. Since input fields are the most common entry point for XSS attack scripts, you must always screen and validate any information that you, your employees, and/or your customers input into data fields³. This is especially crucial if you plan to include the data as HTML output to protect against reflected XSS attacks³. Additionally, you should validate inputs on both the client and server sides as an added precaution³. If you validate the data before it is sent to your servers, you will also benefit from extra protection against malicious XSS scripts³. In short, screening and validating all inputs into your company’s website helps keep attackers at bay. 

Still another way to stop XSS attacks is to install a web application firewall, or WAF, which are especially helpful for filtering bots and other malicious activity, easily thwarting XSS attackers before they can execute any scripts³. In summary, WAFs play a pivotal role in keeping your business’s website and web applications safe. 

Finally, you must have a comprehensive content security policy (CSP) in place to protect against XSS attacks³. CSPs help define the functions your company’s website can perform while preventing it from accepting any in-line scripts. Since your CSP can completely block XSS attacks or at least dramatically reduce their probability, it is an invaluable tool for securing your websites and web applications against these costly, reputation-tarnishing threats to your company³. 

If you are looking to protect your business against harmful XSS attacks, navitend can help. We offer a variety of managed IT support and services for clients throughout New Jersey, New York, and eastern Pennsylvania. With solutions like Immunify web application firewalls (WAFs), plus endpoint encryption and comprehensive security risk assessments, we can help defend your websites and web applications from XSS attacks and their consequences for your business. Our top priority is keeping your data, networks, and applications secure 24 hours a day and seven days a week. 

Navitend can help you. Call 973.448.0070 or setup an appointment today. 


¹IBM Security. “Cost of a Data Breach Report 2022.” Retrieved from

²Bright Security Inc. “XSS Attack: 3 Real Life Attacks and Code Examples” by Oliver Moradov. Retrieved from

³eSecurity Planet. “How to Prevent Cross-Site Scripting (XSS) Attacks” by Kyle Guercio. Retrieved from  

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