I have an Ubuntu desktop. In Ubuntu the Synaptic package manager is always several stable versions behind on Firefox. Moderator Jeanne Boyarsky posted information about a Firefox extension that checks for Heartbleed in the forums here:
but the Ubuntu Firefox version is too old to use it.
I searched the web and found ubuntuzilla,
This is the home of the Ubuntuzilla project, hosts an APT repository with .deb repacks of the latest official release versions of Mozilla Firefox, Mozilla SeaMonkey, and Mozilla Thunderbird. This repository should work on any APT-based distribution