Information disclosure vulnerability in Drupal's Realname User Reference
Widget contributed module (version 6.x-1.0)
 
Discovered by Martin Barbella  
 
Description of Vulnerability:
-----------------------------
Drupal is a free software package that allows an individual or a
community of users to easily publish, manage and organize a wide variety
of content on a website (http://drupal.org/about). 
 
The Realname CCK User Reference Widget module adds a new widget to the
User Reference CCK field type that uses the Realnames for autocompletion
(http://drupal.org/project/realname_userreference). 
 
Only the access content permission is needed to access the page which
displays the user names and real names for users, used by the
autocompletion widget, resulting in an information disclosure
vulnerability.
 
Systems affected:
-----------------
This has been confirmed in version 6.x-1.0 of the Realname User
Reference Widget module.
 
Impact:
-------
This would allow an attacker to collect user names for brute force
attacks, or real names of users for targeted phishing.
 
Mitigating factors:
-------------------
A user must have the access content permission to exploit this
vulnerability, though in most cases even anonymous users would have this
permission.
 
Proof of concept:
-----------------
1. Install the module and its dependencies
2. Configure Realname
3. As any user with access content, visit
realnameuserreference/autocomplete or
realnameuserreference/autocomplete/
4. Note that real names and usernames can be gathered from the output
 
Timeline:
---------
2010-02-01 - Drupal Security notified
2010-02-16 - Still no response from Drupal Security
2010-02-16 - Public disclosure