In the past i've been using the Firefox ESR portable release on all my machines (released by portableapps.com). The ESR edition has been discontinued and now i had to switch to the firefox portable edition lagacy. But fortunately everything went OK: i only had to copy the the browser profiles to the new installations.
July 10, 2018 - 9:23pm
Firefox Portable ESR Switching to 60.x
As per our Firefox Portable ESR schedule, the Firefox Portable ESR channel will be moving up to 60.x tomorrow evening. The Legacy 52 release above is for users who wish to continue testing or using the legacy version of the ESR channel. This Legacy 52 release will be maintained with any security releases made by Mozilla through September 5 according to their standard Firefox ESR release schedule. Keep in mind that this is the last version of Firefox to support legacy extensions. Any users wishing to continue using it should copy their Data directory from FirefoxPortableESR to this new FirefoxPortableLegacy52 branchy. Please note that once your copy of Firefox ESR is upgraded to 60.x, some files will no longer be compatible with the 52.x branch. You can always sync your critical data via Firefox Sync.