ESoft has confirmed, Zango spyware Toolbar was used as a cover for targeting users of Mozilla's Firefox with fictitious browser updates. Providers of fake software are able to use reputable programs illegitimately connecting their software into the install of well known software. These programs are not necessary malicious, but is always unwanted by users. What is more, those programs are gaining to collect information about user without users knowledge.

Source: http://www.spywared.com/security-news/2010/02/05/fraudulent-firefox-update-spreads-via-zango-toolbar.html