Sothink Web Video Downloader contained Win32.LdPinch.gen, and Master Filer contained Win32.Bifrose.32.Bifrose Trojan. Because the trojans are tied to Firefox, Mozilla warns, host computers won't be infected until Firefox started. Uninstalling either add-on is only part of the solution, since the infection had already attacked the host computer. Mozilla recommends that users who suspect they are infected use one of the following security apps to sweep and clean their computers after uninstalling the threatening add-on.
More detail at Mozilla's blog entry
UserAgent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7
