How Cross-Site Scripting Attacks Work and How to Prevent Them

With the prevalence of hacker intrusions, the consequences of not addressing the vulnerabilities and other security loopholes in your network systems could be severe. Adversaries often target unpatched vulnerabilities to compromise targeted systems, and one of their most common attack vectors is Cross-Site Scripting (XSS) attack.

By Rudra Srinivas, Senior Feature Writer, CISO MAG

What is a Cross-Site Scripting (XSS) Attack? 

Cross-site scripting (XSS) attack is an injection attack that allows hackers to inject malicious code into the targeted website or web application. XSS attackers primarily target web pages or web applications that use unsecured processes to validate user inputs. Threat actors often leverage forums, search engines, login forms, comment sections, message boards, and websites that allow user comments to deploy their malicious script via XSS attacks.

How a Cross-Site Scripting (XSS) Attack Works

Cross-site Scripting (XSS) is a common vulnerability observed in websites and web applications that accept user inputs. Threat actors exploit this vulnerability by injecting malicious JavaScript scripts or codes into the targeted website’s URL or content. The malicious scripts automatically deploy and infect the victim’s device when an unsuspecting user visits that website.

Types of Cross-Site Scripting (XSS) Attacks

1. Stored XSS Attack 

Also known as a persistent XSS attack, a Stored XSS attack occurs when an attacker injects a malicious code directly into a vulnerable server. The malware is permanently stored on the targeted servers in repositories such as a database, message forum, visitor logs, and comment sections in stored XSS attacks.

2. Blind XSS Attack 

A blind XSS attack, also known as a persistent XSS attack, occurs when a hacker deploys a malware payload on the targeted server and executes it via backend applications.

3. Reflected XSS Attack 

Reflected XSS attack involves spreading the malicious code via different attack vectors like a phishing email, message, or website. Reflected XSS attackers trick users into clicking malicious links disguised as legitimate content on a compromised website.

Risks of Cross-Site Scripting (XSS) Attacks

Most browsers could fall victim to XSS attacks if the web applications or websites fail to validate the malicious codes inserted by XSS attackers.

An XSS attack could allow an attacker to:

• Steal cookie details
• Alter user settings
• Hijack user sessions
• Turn trusted websites into malicious ones
• Display inappropriate content on the targeted website
• Display malicious content or malware disguised as legitimate content
• Perform impersonation and defacement attacks

How to Prevent Cross-Site Scripting (XSS) Attacks 

Though the consequences of an XSS attack are severe, practicing proper cyber hygiene measures would help mitigate the risks. These include:

• Website developers and owners must ensure that their websites and web applications will validate/sanitize the user inputs before displaying them online.
• Users must avoid clicking/downloading suspicious URLs/attachments online.
• Websites or web applications that accept user inputs must filter unknown code inputs like HTML and JavaScript.
• Regularly scan and address security vulnerabilities on web pages and applications.

About the Author:

Rudra Srinivas is a Senior Feature Writer and part of the editorial team at CISO MAG. He writes news and feature stories on cybersecurity trends.       

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