Understanding AL-Athkat.v2.0 Cross-Site Scripting Vulnerability

What this paper is

This paper, published by indoushka on January 2, 2010, describes a Cross-Site Scripting (XSS) vulnerability found in AL-Athkat.v2.0, a web application. The exploit presented is a proof-of-concept demonstrating how an attacker could inject JavaScript code into the application, which would then be executed in the victim's browser. The primary goal of this specific exploit is to trigger a JavaScript alert() box with a specific number.

Simple technical breakdown

The vulnerability lies in how the AL-Athkat.v2.0 web application handles user input, specifically within the tell_frend.php script. When a user submits information through the tell_frend.php page, the application doesn't properly sanitize or escape certain characters in the input fields.

The exploit targets the name parameter. By injecting HTML and JavaScript code within the name parameter, an attacker can trick the application into embedding this malicious code into the HTML response sent back to the user's browser. When the browser renders this HTML, it will execute the injected JavaScript. In this case, the injected script is alert(213771818860);, which simply pops up a dialog box with the number 213771818860.

Complete code and payload walkthrough

The "code" provided in this paper is not a traditional executable program or script that needs to be run on a server. Instead, it's a crafted URL that exploits a web application's vulnerability. The core of the exploit is the URL itself, which contains the injected payload.

Let's break down the provided exploit URL:

http://server/tell_frend.php?name=indoushka&email=indoushka%40hotmaill%2Ecom&name1=tchalla06@yahoo.fr&email1=Hussin-x&submitok=1&link=&lt;/textarea><ScRiPt%20%0a%0d>alert(213771818860)%3B</ScRiPt>

Here's a breakdown of the components:

• http://server/tell_frend.php: This is the target URL, pointing to a PHP script named tell_frend.php on a web server. This script is likely responsible for handling the "tell a friend" functionality.

• ?: This character separates the base URL from the query parameters.

• name=indoushka: This is a standard parameter, likely for the sender's name. The value "indoushka" is a placeholder.

• &: This character separates different query parameters.

• email=indoushka%40hotmaill%2Ecom: This is the email parameter. %40 is the URL-encoded representation of @, and %2E is the URL-encoded representation of .. This is a standard way to represent characters in URLs.

• name1=tchalla06@yahoo.fr: Another name parameter, likely for the recipient's name.

• email1=Hussin-x: Another email parameter.

• submitok=1: A parameter indicating that the form was submitted.

• link=: An empty link parameter.

• </textarea>: This is where the injection begins. The < is the HTML entity for <, meaning the browser will interpret this as a literal <. So, this part is interpreted as </textarea>. This suggests that the name parameter might be embedded within a <textarea> tag in the original HTML of the page, and this is closing it prematurely.

• <ScRiPt%20%0a%0d>alert(213771818860)%3B</ScRiPt>: This is the core of the XSS payload.

  • <ScRiPt: The start of a JavaScript script tag. The capitalization (ScRiPt) is often used to bypass simple case-sensitive filters.
  • %20: URL-encoded space.
  • %0a: URL-encoded newline character.
  • %0d: URL-encoded carriage return character. These are used to break the script across lines, which can sometimes help evade basic detection.
  • >: The closing bracket of the script tag's opening part.
  • alert(213771818860): This is the JavaScript function call. alert() displays a modal dialog box in the browser. The number 213771818860 is the message displayed in the alert box.
  • %3B: URL-encoded semicolon. This terminates the alert() statement.
  • </ScRiPt>: The closing script tag.

Mapping list:

• http://server/tell_frend.php: Target script for exploitation.
• ?name=indoushka&email=...: Legitimate parameters, potentially used by the script.
• </textarea>: Malicious injection point, likely closing an open <textarea> tag.
• <ScRiPt%20%0a%0d>: Malicious script tag opening, with obfuscation (case variation, whitespace, newlines).
• alert(213771818860)%3B: The actual JavaScript payload to be executed.
• </ScRiPt>: Malicious script tag closing.

Execution Flow:

1. The attacker crafts the malicious URL.
2. The attacker tricks a victim into clicking this URL (e.g., via email, social media).
3. The victim's browser sends a request to http://server/tell_frend.php with the crafted parameters.
4. The tell_frend.php script processes the request. Due to the vulnerability, it directly embeds the content of the name parameter into the HTML output without proper sanitization.
5. The server sends an HTML response back to the victim's browser. This response includes the injected </textarea><ScRiPt%20%0a%0d>alert(213771818860)%3B</ScRiPt> code.
6. The victim's browser parses the HTML and encounters the <ScRiPt> tag.
7. The browser executes the JavaScript code within the tag, displaying alert(213771818860).

Payload Stages:

This exploit has a single stage payload:

• Stage 1: JavaScript Execution (alert(213771818860))
  • Purpose: To demonstrate that arbitrary JavaScript can be executed within the context of the vulnerable web application.
  • Behavior: The JavaScript engine in the victim's browser receives and executes the alert() function.
  • Output: A modal dialog box appears in the browser displaying the number "213771818860".

There is no shellcode or further stages in this particular exploit. The payload is purely client-side JavaScript.

Practical details for offensive operations teams

• Required Access Level: No elevated privileges are required on the target server. This is a client-side attack that exploits how the web server's output is rendered by the client's browser.
• Lab Preconditions:
  • A target web application running AL-Athkat.v2.0 (or a similar version with the same vulnerability).
  • Knowledge of the specific URL path to the vulnerable script (e.g., tell_frend.php).
  • A way to deliver the malicious URL to a user of the target application (e.g., email, chat, social media).
• Tooling Assumptions:
  • A web browser to test the exploit.
  • A URL encoder/decoder might be useful for understanding or crafting payloads.
  • A proxy tool (like Burp Suite or OWASP ZAP) is invaluable for inspecting requests and responses, identifying vulnerable parameters, and testing variations of payloads.
• Execution Pitfalls:
  • WAF/IPS Evasion: Modern Web Application Firewalls (WAFs) and Intrusion Prevention Systems (IPS) are highly likely to detect and block this basic XSS payload due to its common patterns (<script>, alert). The use of case variations (ScRiPt) and URL encoding (%20, %0a, %0d) are rudimentary evasion techniques that might not be effective against sophisticated defenses.
  • Input Sanitization: The target application might have some level of input sanitization that could break the payload. For example, if it strips out <script> tags entirely or encodes < and > characters before rendering.
  • Context of Injection: The exploit relies on the name parameter being directly embedded within an HTML context where a <textarea> tag might be present. If the parameter is used in a different context (e.g., within a JavaScript string literal, an HTML attribute, or a CSS property), the payload would need to be adjusted accordingly.
  • Browser Security Settings: Some browsers might have XSS filters enabled that could prevent the script from executing.
  • User Interaction: The exploit requires the user to click the malicious link. Phishing or social engineering techniques are crucial for delivery.
• Telemetry:
  • Web Server Logs: Look for requests to tell_frend.php with unusual or long name parameters containing script-like characters.
  • WAF/IPS Logs: Alerts related to XSS attempts, script injection, or suspicious URL patterns.
  • Client-Side Monitoring: If endpoint detection and response (EDR) tools are deployed, they might detect unusual browser activity if the XSS payload leads to further malicious actions (though this specific payload only triggers an alert).
  • Network Traffic: Observe HTTP requests containing the crafted URL.

Where this was used and when

• Application: AL-Athkat.v2.0. The paper explicitly mentions testing on Windows SP2 and Linux Ubuntu.
• Timeframe: The paper was published on January 2, 2010. This indicates the vulnerability was active and being exploited around this period. XSS vulnerabilities have been prevalent for many years, and this exploit is representative of common XSS techniques used in the late 2000s and early 2010s.

Defensive lessons for modern teams

• Input Validation and Sanitization: This is the cornerstone of XSS prevention.
  • Validate: Ensure user input conforms to expected formats and types.
  • Sanitize: Remove or encode potentially dangerous characters (like <, >, ', ", /) from user input before it's rendered in HTML. Use robust libraries for this.
• Contextual Output Encoding: Always encode output based on where it will be placed.
  • HTML encoding for data placed within HTML tags.
  • JavaScript encoding for data placed within JavaScript.
  • URL encoding for data placed within URLs.
• Content Security Policy (CSP): Implement CSP headers to restrict the sources from which scripts can be loaded and executed, and to prevent inline scripts.
• HTTPOnly and Secure Flags for Cookies: Prevent client-side scripts from accessing sensitive cookies.
• Web Application Firewalls (WAFs): Use WAFs as a layer of defense, but do not rely on them solely. They are good at catching known patterns but can be bypassed.
• Regular Security Audits and Penetration Testing: Proactively identify and fix vulnerabilities before they can be exploited.
• Keep Software Updated: Ensure all web applications, frameworks, and server software are patched and up-to-date to address known vulnerabilities.

ASCII visual (if applicable)

This exploit is a URL-based attack, so a flow diagram is more appropriate than a structural visual.

+-----------------+     +-----------------+     +-----------------+
| Attacker crafts | --> | Victim clicks   | --> | Victim's Browser|
| malicious URL   |     | malicious URL   |     | sends request   |
+-----------------+     +-----------------+     +-----------------+
                                                        |
                                                        v
+-----------------+     +-----------------+     +-----------------+
| Server sends    | <-- | Vulnerable      | <-- | Web Server      |
| HTML response   |     | script processes|     | (AL-Athkat.v2.0)|
| with injected   |     | input unsafely  |     |                 |
| script          |     +-----------------+     +-----------------+
+-----------------+
        |
        v
+-----------------+
| Victim's Browser|
| executes script |
| (alert box)     |
+-----------------+

Source references

• PAPER ID: 10924
• PAPER TITLE: AL-Athkat.v2.0 - Cross-Site Scripting
• AUTHOR: indoushka
• PUBLISHED: 2010-01-02
• PAPER URL: https://www.exploit-db.com/papers/10924
• RAW URL: https://www.exploit-db.com/raw/10924

Original Exploit-DB Content (Verbatim)

========================================================================================                  
| # Title    : AL-Athkat.v2.0 Cross Site Scripting Vulnerability                    
| # Author   : indoushka                                                               
| # email    : indoushka@hotmail.com                                                   
| # Home     : Souk Naamane - 04325 - Oum El Bouaghi - Algeria -(00213771818860)                                                                     
| # Total alerts found : 1                                                
|                High  : 1                                                                       
|              Medium  :                                                                        
|                  Low :                                                                            
|       Informational  :                                                             
| # Web Site : www.iq-ty.com                                                           
                                                                    
| # Dork     : script AL-Athkat.v2.0 ÓßÑíÈÊ ÇáÃÐßÇÑ v2.0                            
| # Tested on: windows SP2 Français V.(Pnx2 2.0) + Lunix Français v.(9.4 Ubuntu)       
| # Bug      : XSS                                                                     
======================      Exploit By indoushka       =================================
 # Exploit  : 
 
 1- XSS

http://server/tell_frend.php?name=indoushka&email=indoushka%40hotmaill%2Ecom&name1=tchalla06@yahoo.fr&email1=Hussin-x&submitok=1&link=&lt;/textarea&gt;<ScRiPt%20%0a%0d>alert(213771818860)%3B</ScRiPt>


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