Firefox 3.6 EOL

Ever since Mozilla started its controversial new versioning scheme, Firefox 3.6 was still maintained as a stable and supported version of Firefox. Today, Mozilla announced that Firefox 3.6.28, to be released "over the next few weeks", will be the final version of Firefox 3.6. As of April 24th, no more security fixes will be published for Firefox 3.6

Of course, the Firefox version number is at first just a number. One could consider the just released Firefox "11" more like a Firefox 4.11.0 (or 5.11.0). However, plugins and extensions have never quite caught up to the new versioning scheme. 

A Firefox add-on XPI file is a "zip" file, that once unpacked reveals a number of components, including a "install.rdf" file, which among other settings governing the install of the extension lists the range of version numbers for which a certain extension will work. Developers usually do not include future major versions as changes to the extension API and to the Firefox feature set will make it necessary to adapt the extension. This will require extension developers to consistently maintain and update extensions as Firefox releases new major versions.

In some ways, this may be a good thing as this will remove unmaintained extensions. In other ways, developers of valuable extensions may get discouraged by this practice. As a user, you could edit install.rdf file, and modify the range of supported versions. I have done this in a couple cases myself, and had decent succes. However, there is a good chance that this will fail in some cases.

http://blog.mozilla.com/futurereleases/2012/03/23/upcoming-firefox-support-changes/