The vulnerability known as Cross-Site Scripting (XSS) is a widely spread and easily detectable form of attack. It is classified as one of the important vulnerabilities in OWASP TOP 10. XSS occurs when an attacker injects untrusted snippets of JavaScript into an application without validation.
XSS can be executed in three different ways: Reflected XSS, Stored XSS, and DOM-Based XSS. In Reflected XSS, the attacker sends a link to the victim via email or social media. When the victim visits the target site through this link, a script embedded in the link is executed. Stored XSS involves planting a persistent script on the target website, which activates whenever someone visits it. DOM-Based XSS does not require an HTTP request, as the script is injected and executed in the victim’s browser by modifying the DOM of the target site using client-side code.
To understand the concept of XSS better, let’s consider the following example:
http://test.gbhackers.com/search?q=gbhackers
In this case, we are searching for the term “gbhackers,” and the query is reflected in the browser. The untrusted part, “gbhackers,” can be manipulated by an attacker. For instance, they could modify the value to . This simple query could trigger an alert on the webpage if someone requested the attacker’s website page and passed the “document” parameter. If the attacker manages to obtain the user’s authentication cookies, they can potentially hijack their session.
The potential risks of XSS attacks are significant. Attackers can compromise or take over the victim’s user account in the application. They may also retrieve data from the target web application, modify content on the target page, redirect the victim to another malicious site, or install malware on the victim’s system. These consequences can greatly impact a business’s ability to operate, harm its customers, and tarnish its reputation.
To defend against XSS attacks, several measures can be taken. First, it is essential to determine which input can be trusted and ensure it adheres to expected patterns. It is crucial to never reflect untrusted data, including data within the database. Encoding the context of data (Java/attribute/HTML/CSS) is also recommended to mitigate XSS vulnerabilities.
In conclusion, XSS is a prevalent and easily detectable vulnerability that can have severe consequences if exploited. Understanding the different types of XSS attacks and implementing proper defenses is essential in protecting against this threat. Organizations should prioritize XSS prevention measures to safeguard their systems, data, and users from potential harm.