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Cross-site scripting can severely compromise your network security and your company reputation. The most severe XSS (cross-site scripting) attacks allow an attacker to hijack your website visitors’ sessions and take over their accounts.

According to OWASP, an XSS vulnerability could also allow an attacker to change information on your website, with serious consequences. For instance, altering the information in a press release could affect your stock price or damage consumer confidence, or altering dosage information on a pharmaceutical company’s website could cause patients to overdose.

What Is Cross-Site Scripting?

Cross-site scripting occurs when information submitted by the client (in other words, the browser they’re using) is returned back to the user as code within an HTML page. It becomes a problem when the data is a scripting language such as JavaScript.

During an XSS attack, malicious script is injected into a trusted website. An attacker uses a web application to send the script to unsuspecting end users. Users’ browsers can’t tell the script is dangerous, because it comes from a trusted source. When a victim clicks on a link that includes the script, the browser will execute the script.

How Attackers Identify And Take Advantage Of XSS Vulnerabilities

Attackers can find vulnerable web applications by identifying points within your web application where user input is mirrored back to the client. They will attempt to modify the input to include scripting language.

Your web application may be more vulnerable to XSS if it fails to evaluate user input and encodes dangerous tags, which will then prevent the browser from interpreting the malicious input as executable code.

Fixing The Problem

If you own your web application, you can have tests done to identify cross-site scripting flaws and fix them by “sanitizing” user input. You’ll need to convert user input into text that will not be executed.

While your web application users may use browsers with built-in protections against cross-site scripting, or have plug-ins such as NoScript that prevent JavaScript from executing, the onus of preventing attacks is on your company as the web application owner.

Fixing XSS improves the security of the web application because servers use client-side information such as cookies to manage valid user sessions. You can prevent XSS attacks from gaining access to this information and allowing the attacker to hijack a session. Additionally, you can protect against an attacker using the user to modify data and change account information.

If you have XSS vulnerability, fixing it will save your company a lot of trouble. Not only do you minimize the risk of a breach, you’ll be able to focus on other areas that contribute to business growth with peace of mind that your network and users are protected.

Ready to learn more about how you can protect your network? Discover three reasons you need internal penetration testing in addition to external testing.