PR07-21: Webbler CMS forms are susceptible to spamming and phishing abuses

This advisory has been published following consultation with UK CPNI (formerly known as NISCC) 

Date Found: 14th June 2007


Successfully tested on: Webbler CMS version 3.1.3. Earlier versions are possibly affected as well.

Note: the version number is usually included within 'meta' HTML tags and 'X-Powered-By' HTTP response headers. i.e.:

<meta name="generator" content="webbler 3.1.3 - http://tincan.co.uk/webbler" />

X-Powered-By: webbler version 3.1.3 


Description:

Webbler CMS "mail a friend" forms are susceptible to spamming and phishing abuses. 
Such forms are designed to email links from the target site to friends.  
 
Lack of restrictions on user-supplied input allow attackers to send emails from spoofed email addresses without restrictions on the number of recipients to be emailed. 
 

Consequences:

It is common for spammers to exploit email forms that lack restrictions on user-supplied input. In this case a spammer could write a script that automatically sends emails to as many email addresses as desired. Although the 'code' parameter is different with each form submitted, the value of such code could be obtained for each request by programmatically visiting the URL where the "mail a friend" form is located.

The following is an example of a "mail to friend" form (partial output has been omitted for clarity purposes):

        <form method="post" action="http://www.target-domain.com/?lid=12506">
        <input type="hidden" name="code" value="4672577a2d323">
        <input type="hidden" name="referral_uri" value="">
        <input type="hidden" name="document_title" value="">
  <input type="text" name="recipient" value="">
  <input type="text" name="username" value="">
  <input type="text" name="useremail" value="">
  <INPUT class="sendbutton" type=submit name=sa VALUE="send page">
  </form>
 
Attackers can also abuse the form for phishing purposes. The fact that the sender's email address can be set to any value makes the form ideal for phishing attacks. 

For instance, an attacker could launch a phishing attack against the target site's employees by setting the sender's email address to 'admin@target-domain.com'.
  

Successfully tested on:

Server environment:

Webbler CMS 3.1.3
PHP 5.1.6
Apache web server (unknown version)


Severity: Medium


Author: Adrian Pastor of ProCheckUp [adrian.pastor [at] procheckup.com]

ProCheckUp thanks Tincan for fixing this vulnerability so promptly.


References:

http://tincan.co.uk/webbler
http://tincan.co.uk/?lid=1975
http://www.procheckup.com/Vulner_2007.php


Fix:

This issue has been fixed on version version 3.1.6.


Legal:

Copyright 2007 ProCheckUp Ltd. All rights reserved.

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Any other use of this information is prohibited. ProCheckUp is not liable for any misuse of this information by any third party.