XSS has been plaguing web application security for a long time . XSS lets attackers inject malicious scripts into web pages, compromising passwords, credit card numbers, and other sensitive data. XSS attacks can lead to  financial loss, identity theft, and permanent damage to a company’s reputation.

This article will discuss XSS attacks, their types, real-world examples, and attackers’ methods. Web application development best practices, third-party vendor tools, and CSP to prevent XSS attacks will also be discussed.

Types of XSS Attacks

Stored and reflected XSS attacks are the most commonly known types.

Stored XSS

Stored XSS, also known as persistent XSS, occurs when the malicious script is permanently stored on the target web server and served to all users who visit the affected page. This XSS attack can affect many users over time, making it dangerous.

The Samy worm was one of the first widely publicized stored XSS attacks. Samy Kamkar used a stored XSS vulnerability in MySpace to spread a worm that added “but most of all, samy is my hero” to all of the user’s friends’ profiles in 2005. The worm infected millions of profiles in hours.

Reflected XSS

Reflected or non-persistent XSS attacks execute the attacker’s malicious script in the user’s browser. Reflected XSS is only executed when the user visits the page, unlike stored XSS.

A search engine that fails to validate user input allows an attacker to inject malicious scripts into search results, a reflected XSS attack. The attacker could steal passwords and credit card numbers using this vulnerability.

Real-World XSS Attacks

XSS attacks stole LinkedIn users’ personal data in 2010. The job search feature was exploited to inject malicious scripts that stole users’ login credentials.

A similar XSS attack stole Steam users’ personal data in 2011. The site’s forums were exploited to inject malicious scripts that stole users’ login credentials.

CryptoLocker spread via XSS in 2013. A legitimate software company’s website was exploited to inject a malicious script that redirected users to CryptoLocker malware.

A 2014 XSS attack stole eBay users’ personal data. The site’s search feature was exploited to inject malicious scripts that stole users’ login credentials and other sensitive data.

These real-world examples demonstrate the seriousness of XSS attacks and the need for organizations to protect their web applications and users.

Attacker Tools

XSS attacks use automated tools, custom scripts, and browser extensions. Attackers use:

XSSer: An open-source XSS attack automation tool for web application security testing.

BeEF: A browser exploitation framework that lets hackers steal sensitive data and run malicious scripts.

OWASP Xenotix XSS Exploit Framework: This framework is used to test web application XSS security.

XSS-Payload-List: collection payloads to implement XSS.

How to prevent XSS

Web application development best practices and security tools and technologies prevent XSS attacks. Preventing XSS attacks involves:

Validating and sanitizing user input before the web application processes it.

Content Security Policy (CSP): Restricting web application scripts to reduce XSS attacks.

Third-party vendor tools, such as WAFs, to detect and block XSS attacks.

Web application security testing: finding and fixing vulnerabilities, including XSS attacks.

These best practices and tools can protect web applications and users from XSS attacks and make them much less likely to happen.

Conclusion

Cross-Site Scripting (XSS) is still a serious web application security issue today. XSS attacks can cause annoyance, financial loss, identity theft, and permanent brand damage. Web application development best practices, third-party vendor tools, and security technologies like Content Security Policy (CSP) can prevent XSS attacks.

XSS attacks will increase as the internet becomes more complex. Organizations must stay informed and protect their web applications and users from these threats.