In a Bugzilla report, Mozilla has revealed that they provide enterprise MSI installers starting with Firefox 65. System administrators can create their own transform files (MST) to easily customize the installation of Firefox in their organization. A MST file is a file that contains the changes that an administrator wants to apply to an installer. An administrator can create a customized installation that is then pushed out to all of the users in the organization. The decision to offer an MSI installer for Firefox is to make it easier to deploy the browser in the enterprise.
Source: https://www.bleepingcomputer.com/news/software/mozilla-to-provide-msi-installers-starting-with-firefox-65/