Whitepaper on Xenotix XSS Exploit Framework

1. Detecting and Exploiting XSS with
Xenotix XSS Exploit Framework
Ajin Abraham
ajin25@gmail.com
ajinabraham.com
keralacyberforce.in
Introduction
Cross Site Scripting or XSS vulnerabilities have been reported and exploited since 1990s. XSS got
listed as the top 2nd Vulnerability in the OWASP 2010 Web application Vulnerabilities list.
Figure 1: Top 10 Web Application Vulnerabilities OWASP
Cross-site scripting (XSS) is a type of security vulnerability typically found in web applications which
allows the attackers to inject client-side script into web pages viewed by other users. The execution
of the injected code takes place at client side. A cross site scripting vulnerability can be used by the
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2. attacker to bypass the Same Origin Policy (SOP). In the past, the potentials of XSS vulnerability were
not known. XSS was mainly used for stealing cookies and for temporary or permanent defacements
and was not considered as high risk vulnerability. But later XSS tunneling and Payload delivering
showed us the potential of XSS Vulnerability. Most of the large websites like Google, Facebook,
Twitter, Microsoft, and Amazon etc. even now suffers from XSS bugs. That’s a brief introduction
about XSS.
Threats due to XSS
XSS Tunneling: With XSS Tunnel a hacker will obtain the traffic between the victim and a
webserver.
Client side code injection: A hacker can inject malicious codes and execute them at client side.
DOS: A hacker can perform DOS against a remote server or against the client itself.
Cookie Stealing: A hacker can obtain the session cookies or tokens of a victim.
Malware Spreading: A hacker can spread malwares with a website which is vulnerable to XSS.
Phishing: A hacker can embed or redirect to a fake page of the website to get the login
credentials of the victim.
Defacing: Temporary or permanent defacement of web application is possible.
Need for a new Tool
Many tools are available for detecting XSS vulnerabilities in web applications. But most of these
are not so easier to use or you should specify XSS payloads manually. I found many Penetration
testers just using <script>alert(‘XSS’)</script> or <script>alert(document.cookie)</script> as the
POC for the detected XSS vulnerability which often fails to create an impression on their clients
that XSS is a severe threat. So I thought of the possibility of a new user friendly tool with a
payload list to test against XSS in a web application and an XSS Exploitation Framework. After a
5 months research, I built a XSS payload database of over 500+ XSS payloads and implemented
a tool in VB.NET and that is Xenotix XSS Exploit Framework.
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3. What is Xenotix XSS Exploit Framework?
Figure 2: Xenotix XSS Exploit Framework
Xenotix XSS Exploit Framework is a penetration testing tool to detect and exploit XSS
vulnerabilities in Web Applications. This tool can inject codes into a webpage which are
vulnerable to XSS. It is basically a payload list based XSS Scanner and XSS Exploitation kit. It
provides a penetration tester the ability to test all the XSS payloads available in the payload list
against a web application to test for XSS vulnerabilities. The tool supports both manual mode
and automated time sharing based test modes. The exploitation framework in the tool includes
a XSS encoder, a victim side XSS keystroke logger, an Executable Drive-by downloader and a XSS
Reverse Shell. These exploitation tools will help the penetration tester to create proof of
concept attacks on vulnerable web applications during the creation of a penetration test report.
Features of Xenotix XSS Exploit Framework
The features of Xenotix XSS Exploit Framework are
 Built in XSS Payloads
 Automated Testing
 XSS Keylogger
 XSS Executable Drive-by downloader
 XSS Payload Encoder
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4.  XSS Reverse Shell
 XSS DDoSer
 XSS Cookie Thief
Built in Payload List
It is having an inbuilt XSS payload list of above 500+ XSS payloads. It includes HTML5
compactable XSS injection payloads. Most of the XSS filters are implemented using String
Replace filter, htmlentities filter and htmlspecialcharacters filter. Most of these weakly designed
filters can be bypassed by specific XSS payloads present in the inbuilt payload list.
Figure 3: XSS Payload count in different Vulnerability Scanners
The above chart shows the number of XSS Payloads in different XSS Scanning tools available in
market. Xenotix XSS Exploit Framework got the world’s second largest XSS Payload list after IBM
AppScan Security which is having 700 million payloads.
Automatic XSS Testing
The tool is having an automatic test mode based on a time interval. You have to specify the
time interval according to the time taken by a webpage to load which depends on your
bandwidth. It will test all the payloads one by one after the specified time interval. With this
feature automated XSS testing can be done. You don’t have to check all the 500+ payloads
manually.
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5. XSS Keylogger
Figure 4: XSS Keylogger Working
The tool includes an inbuilt victim side Key logger which is implemented using JavaScript and
PHP. PHP is served with the help of a portable PHP server named QuickPHP by Zach Saw. A
JavaScript file is injected into the web application vulnerable to XSS and is presented to the
victim. The script captures the keystrokes made by the victim and send to a PHP file which
further write down the logs into a text file.
XSS Executable Drive-by Downloader
Figure 5: Executable Drive-by Downloader Working
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6. Java Drive-by download can be implemented with Xenotix XSS Exploit Framework. It allows the
attacker to download and run a malicious executable file on the victim’s system without his
knowledge and permission. You have to specify the URL for the malicious executable and then
embed the drive-by implemented webpage into a XSS vulnerable page and serve your victim.
When the victim view the injected page, the java applet client.jar will access the command
prompt and with the help of echo command, write down some scripts to a Visual basic script
file named winconfig.vbs in the temp directory(%temp%) and then the cmd.exe will start
winconfig.vbs. The winconfig.vbs will download the malicious executable specified by you in the
URL to temp directory and rename it as update.exe and finally it will execute update.exe. The
downloading and executing of the malicious executable happened without the knowledge and
permission of the victim.
XSS Payload Encoder
The inbuilt Encoder will allow encoding into different forms to bypass various filters and Web
Application Firewalls. The encoder supports Base64 Encoding, URL Encoding, HEX Encoding,
HTML Characters Conversion, Character Code Conversion and IP to Dword, Hex and Octal
conversions.
XSS Reverse Shell
A XSS Reverse Shell can be implemented with Xenotix XSS Exploit Framework. This is made
possible with the help of Java Drive-By. The XSS vulnerable web application exploited with the
injectable scripts generated by XSS Reverse Shell when presented to a victim will initiate the
drive by download of a Reverse TCP connecting shell. After the drive-by download, the reverse
shell is executed by the same method used in Java Drive-by.
Figure 6: Establishing a reverse shell by exploiting XSS in web applications.
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7. The advantage of this method is that the reverse shell is downloaded and executed in the
victim’s system without his knowledge. But for the execution of reverse shell, it will pop up a
UAC dialog requesting for the permission to run the executable. The tool is having an inbuilt
Listener that listens to the reverse shell. It is designed in a user friendly manner. All you have to
do is to specify the reverse connection IP and port.
XSS DDoSer
Figure 7: Distributed Denial of Service Attack with Xenotix XSS Exploit Framework
With HTML 5 comes great power. We harvest the power of HTML 5 to abuse the Cross Origin
Resource Sharing (CORS) and WebSocket to implement a DDoS attack. WebSocket is a technology
that allow web applications to have a bidirectional channel to a URI endpoint. Sockets can send and
receive data to and from a web server and respond to opening or closing a WebSocket. The
XMLHttpRequest is a JavaScript object which is used to exchange data between a server and a
bowser behind the scene. This can be used for Cross Origin Resource Sharing (CORS). We can
perform a combined and powerful DDoS attack by abusing these two technologies. This module
abuses WebSocket and creates numerous socket connections with a target server to slow it down.
Along with it by abusing CORS, the add-on create numerous fake GET requests to slow down the
target server. When we send the first request to the target server and the response does not contain
the 'Access-Control-Allow-Origin' header with a suitable value then at times the browser refuses to
send more requests to the same URL. However this can be easily bypassed by making every request
unique by adding a non-existing query-string parameter with changing values.
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8. XSS Cookie Thief
Figure 8: XSS Cookie Thief Console
It’s the traditional Cookie Stealer but a bit advanced and with real time cookie viewer. This
module allows the pentester to create cookie stealing POC.
Testing a website with Xenotix XSS Exploit Framework
To test a website URL, say http://www.site.com/search.php?id=1&term=about
Suppose you suspect that the variable ‘term’ is vulnerable to XSS.
Figure 9: Testing a Website with Xenotix XSS Exploit Framework
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9. For testing against XSS in Xenotix XSS Exploit Framework you should specify the protocol, which
is http or https. Then give the website URL other than the suspected variable in the field after
the protocol and specify the suspected variable in the Variable to test field. Now select
between Inbuilt XSS Payloads or Custom XSS payloads. You can select between Manual Mode
and Auto Mode to start testing.
Features for the Next Build
Current version of XSS Exploit Framework is based on Internet Explorer’s webpage rendering
engine Trident. Since XSS got slightly different behavior in different Web Browsers, the support
for the Gecko (Used by Mozilla Firefox) and Webkit (used by Chrome, Opera, and Safari)
Rendering engines will be added up in the next build. The support for XSS in POST Parameter
and XSS testing by modifying the headers will be included in the next build. XSS Proxy to tunnel
the victim-server traffic will be added in future builds. Automatic detection of parameters or
variables vulnerable against XSS and DOM Based XSS detection will be added up in next build.
Conclusion
XSS in popular website is a high security threat. Xenotix XSS Exploit Framework can be used by
Security Analysts to perform penetration test on Web Applications against XSS vulnerability and
to create POC with the inbuilt exploitation framework. Most of the security tools related to XSS
are either XSS Scanners or XSS Exploitation tools. Xenotix XSS Exploitation Framework is the
first of its kind to act both as an XSS vulnerability scanner as well as XSS exploitation framework.
Bug bounty programs like Google Vulnerability Reward Program, Facebook Bounty, Paypal bug
bounty etc. are there. So go for a XSS hunting and grab your bounty. 
Download: https://www.owasp.org/index.php/OWASP_Xenotix_XSS_Exploit_Framework
References
Papers
 Our Favorite XSS Filters/IDS and how to Attack Them - Eduardo Vela and David Lindsay.
 Blackbox Reversing of XSS Filters - Alexander Sotirov.
 Advanced Cross-Site-Scripting with Real-time Remote Attacker Control - Anton Rager
 Bypass XSS filters - k3nz0
 XSS for Fun and Profit - Lord Epsylon
 Bypassing Web Application Firewalls (WAFs) - Ing. Pavol Lupták
 Abusing Internet Explorer 8’s XSS Filters –Eduardo Vela Nava, David Lindsay
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10. Websites
 OWASP’s Cross-site Scripting (XSS)
https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)
 CGISecurity's Cross Site Scripting FAQ
http://www.cgisecurity.com/xss-faq.html#
 Gunter Ollmann's XSS paper
http://www.technicalinfo.net/papers/CSS.html
 PeterW's Cross Site Request Forgery (CSRF) Concept
http://www.securityfocus.com/archive/1/191390
 CERT info on XSS
http://www.cert.org/advisories/CA-2000-02.html
 Remote Scripting with IFRAMEs
http://developer.apple.com/internet/webcontent/iframe.html
 HTML5 Security Cheat sheet
http://html5sec.org/#html5
 Cross Site Scripting - XSS - The Underestimated Exploit
http://www.acunetix.com/websitesecurity/cross-site-scripting.htm
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