Reply To: Why is that? My Firefox DisableAppUpdate is true?

Let me explain something before this thread becomes any one of the other related threads found in mx linux forum.

MX linux packages their own debs (Debian installation package files). They can be installed and updated from the MX Package Installer.
If you install something from the MX package installer it will be supported either by Debian or by the MX team, so all updates depend on them packaging the software. They first test the software and, once they are happy with the results, they package it. They may have it wait some time in the test repo and, once they think everything is stable and OK, they add it to the stable repo. Then, you receive an update notification for said package and you happily install it.

Your firefox installation is supported by the MX team, so the updates are locked to only the ones coming from the MX repo. They do this to avoid that a new official firefox version (untested in debian or MX) gets installed as an update and breaks your firefox/system, and then you or someone else goes to the forum complaining about this update and demanding the MX team to fix it.

If you are unhappy with the version packaged by the MX team, you can remove firefox (using the MX package installer) and download it directly from Mozilla’s site (http://www.mozilla.org/firefox/all/#product-desktop-release). This is a tarball file containing the firefox binaries that you will have to install manually (it is NOT a .deb file), so all support and installation is up to you. Here you have instructions for installing in Debian:
http://wiki.debian.org/Firefox#From_Mozilla_binaries

Another (temporary) solution is to delete the profiles.json file inside the firefox folder, but this solutions will only last until MX linux next firefox update.

It is up to you to decide what to do with this information.