According to Mozilla, version 4.0 of Sothink Web Video Downloader is infected with password sniffer Win32.LdPinch.gen and Master Filer is infected with the backdoor Trojan Win32.Bifrose. This Malware has infected Windows systems following installation of the infected browser add-on.
Uninstalling the add-on will not remove the infection from your computer. Mozilla lists several anti-virus programs in its advisory that are able to recognize the Malware and remove it from the infected computer.
Both infected add-ons have been downloaded a total of 4,600 times from the Mozilla official download site. The infected add-ons were only discovered and removed, on January 25 and February 2, following use of additional anti-virus scanning software by Mozilla.
Users shouldn’t panic as only a small amount of computers were infected. It’s more than likely that your antivirus software will recognize and remove the infection.