Saw posted at
Viruses not just a Windows issue
According to a report from antivirus company Kaspersky, Mozilla.org recently hosted Linux versions of the Mozilla browser and Thunderbird mail client that were infected with the Linux RST.b virus.
But if you follow the links contained you find at
Analyst's Diary Infected files found on mozilla site

many disgruntled members concerning the reporting.

At
Mozilla Security Center
there is
Security Advisory (September 21, 2005) The Mozilla Foundation is aware of the Linux.RST.b virus that infected Linux Korean contributed versions of Mozilla Suite 1.7.6 and Thunderbird 1.0.2, as reported by Kaspersky Lab. No versions of Mozilla Firefox were infected. Infected files have been removed from the Mozilla ftp mirror network as of September 17.

Mozilla recommends to our Korean users who have downloaded affected products to run an AntiVirus product on their machine to scan for the Linux.RST.b virus and delete infected files. Further information about the Linux.RST.b virus can be found here: http://us.mcafee.com/virusInfo/defau...&virus_k=99978
So apparently it was a mirror site that contained the infected files. No word as to how they got there, but just something to be aware.