"Google has detected user-generated spam on your site. Typically, this kind of spam is found on forum pages, guestbook pages, or in user profiles. As a result, Google has applied a manual spam action to your site."
The blame has been placed on spammers abusing the blog comments and the add-ons section of the site.
Following from Interflora's high-profile penalty in February for "suspicious" link-building. With Mozilla's offence being of a very different nature, Google only penalised the illegal pages from their search rankings as opposed to the the entire site.
0 comments