H-Online: Security specialist Sophos reports that it has discovered new spam email messages that claim to be an advisory related to an update to the open source Firefox web browser. The fake advisory asks users to update their Firefox installations, “for security reasons”, and includes a download link to the supposed update.

According to Graham Cluley of Sophos, the download leads to an executable file that bundles an installer for the Windows version of Firefox 5.0.1 and a password-stealing trojan (Troj/PWS-BSF). As noted by Cluley, users should always exercise caution when clicking on links in emails.

Users can download the latest stable version of Firefox directly from the Mozilla project. Alternatively, users can upgrade to the new versions either by waiting for the automated update notification or by manually selecting “Check for updates” from the Help Menu.