GitHub XSS Vulnerabilities: Armorcode Testing Discussion

Oct 20, 2025 by ADMIN 57 views

Cross-Site Scripting (XSS) Vulnerabilities on GitHub: Armorcode Testing Discussion

Hey guys! Today, we're diving deep into Cross-Site Scripting (XSS) vulnerabilities identified during Armorcode testing on GitHub. We'll break down two specific instances, explore their backgrounds, remediation strategies, and provide references for further learning. So, grab your favorite beverage, and let's get started!

Reflected XSS in /bank/customize.jsp

Let's kick things off by examining a high-severity reflected Cross-Site Scripting (XSS) vulnerability discovered in the /bank/customize.jsp page of a test application. This vulnerability highlights the dangers of unsanitized user input and how it can be exploited to inject malicious JavaScript code.

Issue Details

The core of the problem lies in how the application handles the lang request parameter. The value provided for this parameter is directly copied into the HTML document as plain text between tags. This means that if an attacker can control the lang parameter, they can inject arbitrary HTML and JavaScript into the page. In this specific case, the payload dlf8h<script>alert(1)</script>ei1jm was submitted via the lang parameter, and the application echoed this input without any modification. This simple proof-of-concept demonstrates the potential for executing arbitrary JavaScript within the user's browser.

Background: Understanding Reflected XSS

So, what exactly is reflected Cross-Site Scripting (XSS), and why is it so dangerous? Reflected XSS vulnerabilities occur when data from a client's request is immediately echoed back by the application in an unsafe manner. This means the malicious script isn't stored on the server itself (unlike stored XSS), but it's reflected off the web server back to the user's browser. An attacker crafts a malicious URL containing the JavaScript payload and tricks a user into clicking on it. When the user's browser sends the request, the server reflects the malicious script back to the user, and the browser executes it.

Think of it like a mirror reflecting an image – the malicious script bounces off the server and impacts the user directly. The consequences can be severe, ranging from stealing session tokens and login credentials to performing actions on the user's behalf and even logging their keystrokes. Attackers can use various techniques to induce users to click on these malicious links, such as embedding them in emails, instant messages, or even seemingly harmless websites.

Remediation: How to Prevent Reflected XSS

The good news is that reflected Cross-Site Scripting (XSS) can be prevented with a robust defense strategy. The key is to implement two layers of protection:

Strict Input Validation: The first line of defense is to rigorously validate user input on arrival. This means defining strict rules for the type of data expected and rejecting anything that doesn't conform. For example, if you're expecting a name, validate that it consists of only alphabetical characters and a limited set of punctuation. If you're expecting a year, ensure it's exactly four numerals. Importantly, any input that fails validation should be rejected outright, not sanitized.
HTML Encoding on Output: The second crucial step is to HTML-encode user input at any point where it's included in the application's response. This involves replacing HTML meta-characters like <, >, ", ', and = with their corresponding HTML entities (<, >, ", ', and =). This ensures that the browser interprets these characters as literal text rather than HTML code, effectively neutralizing any malicious scripts.

In scenarios where users are allowed to author content with a limited subset of HTML tags (like in blog comments), you'll need to parse the HTML and validate that it doesn't contain any dangerous syntax. This is a more complex task, but it's essential for maintaining security.

References for Further Learning

Want to dive deeper into Cross-Site Scripting (XSS)? Here are some valuable resources:

Vulnerability Classifications

This vulnerability falls under several common weakness enumerations (CWEs):

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
CWE-116: Improper Encoding or Escaping of Output
CWE-159: Failure to Sanitize Special Element
CAPEC-591: Reflected XSS

Request and Response Example

Here's a look at the HTTP request and response that triggered the vulnerability:

Request:

GET /bank/customize.jsp?content=customize.jsp&lang=englishdlf8h%3cscript%3ealert(1)%3c%2fscript%3eei1jm HTTP/1.1
Host: demo.testfire.net
Cookie: JSESSIONID=3158E52150C3448293D0D05F878E20B6; AltoroAccounts=ODAwMDAwfkNvcnBvcmF0ZX41LjIzNDE2MDc2MUU3fDgwMDAwMX5DaGVja2luZ34yMDkyMDkuNDR8
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Upgrade-Insecure-Requests: 1
Referer: https://demo.testfire.net/bank/customize.jsp
Accept-Language: en-US;q=0.9,en;q=0.8
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.41 Safari/537.36
Connection: close
Cache-Control: max-age=0
Content-Length: 0

Response:

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: text/html;charset=ISO-8859-1
Content-Length: 5820
Date: Wed, 11 May 2022 11:11:59 GMT
Connection: close

<!-- BEGIN HEADER -->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1
...
<p> Current Language: englishdlf8h<script>alert(1)</script>ei1jm </p>
...

Notice how the injected script is echoed back in the response, demonstrating the vulnerability.

Reflected XSS in /bank/queryxpath.jsp

Next up, we'll analyze another instance of reflected Cross-Site Scripting (XSS), this time found in the /bank/queryxpath.jsp page. This case presents a slightly different scenario, as the injected payload is placed within an HTML tag attribute.

Issue Details

In this vulnerability, the value of the query request parameter is copied into the value of an HTML tag attribute, specifically within double quotation marks. The payload n5m6i"><script>alert(1)</script>h2q9g was submitted through the query parameter. Again, the application echoed this input without any modification, showcasing the possibility of injecting arbitrary JavaScript.

Background: XSS in HTML Attributes

This example illustrates a common variation of Cross-Site Scripting (XSS) where the malicious script is injected within an HTML attribute. While the fundamental principle remains the same – exploiting unsanitized user input – the context changes the attack vector slightly. By injecting the script within an attribute, attackers can often bypass basic input validation measures that might only focus on the content between HTML tags.

Remediation: Consistent Application of Security Measures

The remediation strategy for this vulnerability is essentially the same as for the previous one: a combination of strict input validation and proper HTML encoding. Remember, consistency is key in security. Applying these measures across your entire application is crucial to prevent Cross-Site Scripting (XSS) and other injection-based attacks.

Request and Response Example

Let's examine the HTTP request and response for this vulnerability:

Request:

GET /bank/queryxpath.jsp?content=queryxpath.jsp&query=Enter%20title%20(e.g.%20Watchfire)n5m6i%22%3e%3cscript%3ealert(1)%3c%2fscript%3eh2q9g HTTP/1.1
Host: demo.testfire.net
Cookie: JSESSIONID=5B8AC38828EF66CA27B7E2A06819BA14; AltoroAccounts=ODAwMDAwfkNvcnBvcmF0ZX41LjIzNDE2MDc2MUU3fDgwMDAwMX5DaGVja2luZ34yMDkyMDkuNDR8
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Upgrade-Insecure-Requests: 1
Referer: https://demo.testfire.net/bank/queryxpath.jsp
Accept-Language: en-US;q=0.9,en;q=0.8
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.41 Safari/537.36
Connection: close
Cache-Control: max-age=0
Content-Length: 0

Response:

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: text/html;charset=ISO-8859-1
Content-Length: 5893
Date: Wed, 11 May 2022 11:06:40 GMT
Connection: close

<!-- BEGIN HEADER -->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1
...
<input type="text" id="query" name="query" width=450 value="Enter title (e.g. Watchfire)n5m6i"><script>alert(1)</script>h2q9g"/>
...

In this case, the injected script is embedded within the value attribute of an input tag, further illustrating the importance of encoding all user-controlled data in the output.

Key Takeaways and Conclusion

Alright, guys, we've covered a lot of ground today! Let's recap the key takeaways:

Cross-Site Scripting (XSS) is a serious vulnerability that can have significant consequences.
Reflected Cross-Site Scripting (XSS) occurs when user input is immediately echoed back in an unsafe manner.
Strict input validation and proper HTML encoding are essential for preventing Cross-Site Scripting (XSS).
Consistency in applying security measures across your application is paramount.

By understanding the mechanics of Cross-Site Scripting (XSS) and implementing robust defenses, we can significantly improve the security posture of our applications. Keep learning, stay vigilant, and let's build a more secure web together!