source: http://www.securityfocus.com/bid/26977/info

MRBS is prone to an SQL-injection vulnerability because it fails to sufficiently sanitize user-supplied data before using it in an SQL query.

Exploiting this issue could allow an attacker to compromise the application, access or modify data, or exploit latent vulnerabilities in the underlying database.

This issue was previously documented as a vulnerability in Moodle. Further reports indicate this issue affects MRBS, and the MRBS module for Moodle. 

http://www.example.com/PATH/moodle/ing/blocks/mrbs/code/web/view_entry.php?id=2000%20UNION%20SELECT%20username,id,id,id,id,id,id,id,id,id,id,id%20FROM%20mdl_user%20WHERE%20id=[ID]&day=27&month=10&year=2007 