Here are a news about trojan from Greasemonkey – a Firefox addon. It is identified by BitDefender.
BitDefender has identified this new bit of holiday cheer as Trojan.PWS.ChromeInject.A” (the ChromeInject suffix refers to the Chrome component of Firefox). The trojan installs itself into Firefox’s add-on directory, registers itself as Greasemonkey, and begins searching your hard drive for passwords, login details, your World of WarCraft account information, and your library card number.