fuel/core — pull request #656 by ipalaus (2011-11-09 13:55:25+00:00)
Title: Ensure that the variables are strings and prevents injections on the Mongo query

According to that document http://www.idontplaydarts.com/2010/07/mongodb-is-vulnerable-to-sql-injection-in-php-at-least/

And this references in php.net: http://php.net/manual/en/mongo.security.php

This is the way to prevent attacks of user input.