Uncovering Cross-Site Scripting Vulnerabilities

Introduction:

In today's interconnected digital landscape, web security is paramount. One of the most common vulnerabilities encountered by web developers and security professionals alike is Cross-Site Scripting (XSS). In this blog post, we'll explore a real-world example of an XSS vulnerability discovered through analyzing HTTP requests and responses.

let's consider the domain as abc.com

Request Analysis:

Let's start by examining a typical HTTP request captured by a web proxy tool like BurpSuite. The request targets a URL related to financial services, specifically a car loan calculator. Here's a snippet of the request:

GET /abc/loan/car/?hasInitialValues="><script>alert(document.cookie)</script> HTTP/1.1

Host: www.abc.com

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8

Response Analysis:

Upon sending this request to the server, we receive an HTTP response. Here's a snippet of the response:

HTTP/1.1 200 OK

Content-Type: text/html; charset=utf-8

<link rel="canonical" href="/abc/loan/car/?hasInitialValues="><script>alert(109)</script>">

Notice the `<link rel="canonical">` tag in the response. This tag is typically used to specify the preferred URL for a web page. However, in this case, it contains a suspicious script tag inserted directly into the `href` attribute. This indicates a potential XSS vulnerability.

Testing for Vulnerability:

To confirm the vulnerability, we can manually inject a harmless script into the URL and observe the server's response. For example:

https://www.abc.com/marketplace/loan/car/?hasInitialValues="><script>alert('109')</script>

Conclusion:

The example discussed highlights the importance of thorough web security testing. XSS vulnerabilities can have serious consequences, including data theft, session hijacking, and malware distribution. By understanding how to analyze HTTP requests and responses, developers and security professionals can better protect web applications from such threats.

In future posts, we'll delve deeper into XSS prevention techniques and explore advanced security measures to safeguard against emerging threats in the ever-evolving landscape of web security. Stay tuned for more insights and best practices to secure your web applications effectively.