Why is the version in the Mozilla add-on store out of date?
You may notice that the most up to date versions are not always available at the same time for all browsers when updates are pushed out automatically or if you go to the browser's add-on/extension store. This occurs because, after we update LastPass and submit it to the respective browser's stores, they must approve of the changes first. Then, it is up to the browser to push these updates out automatically. This can take some time.
Users have reported some frustration at the lack of updates for the Firefox add on through the official store. We submit new builds as we create them and our rapid release cycle means that we are submitting builds every few days or weeks. This means that if Mozilla has not completed their review, the process must start over for the new build. You can see how the AMO team is doing by checking out their review queue stats here: https://forums.mozilla.org/viewforum.php?f=21