Unless the offending malware gets removed, when using Firefox it will be classified as a 'Reported Attack Site'. Basically, whoever runs the site/server will need to remove any malware/dodgy software and wait for the google system to scan it and see it is safe again for the worning to be removed.
Generally, this happens when a script kiddy compromises a site due to software versions in use on it are not being kept up to date.
