Two add-ons for popular Open Source web browser Firefox have been downloaded by thousands of unsuspecting users, according Mozilla.
A security post on the campany's blog warns that two experimental plug-ins - version 4.0 of Sothink Web Video Downloader and all versions of Master Filer were found to contain Trojan code aimed at Windows users.
"If a user installs one of these infected add-ons, the trojan would be executed when Firefox starts and the host computer would be infected by the trojan. Uninstalling these add-ons does not remove the trojan from a user’s system", said the blog's unnamed author.
The infected add-ons, which have been downloadable from as long ago as February 2008, were only spotted when Mozilla recently updated its malware detection tools.
Anyone who thinks they may have caught a cold from this lapse in security should use one of the anti-virus programmes listed here.