User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:66.0) Gecko/20100101 Firefox/66.0
Steps to reproduce:
We are running a massive multi-user Linux deployment with Firefox. When a new version of Firefox is released, we install the tarballs into a few folder and then move users to the new binary. If there is a problem we can immediately rollback, and we keep old versions for this very reason. We upgraded to Firefox 67 just minutes ago, and many users started to pick up the new binary.
In some way, it perceived we wanted to run multiple versions of Firefox and built them brand new profiles and all of their passwords and profiles were "lost" from their view and of course we received support calls. I immediately did a rollback to FF 66 and it located their previous profiles.
In our case, this new feature is not desired and we are seeking a way to not have Firefox attempt to create new profiles for each detected version. I don't see an about:config way to do this.
I am not sure what mechanism is used to figure out if you have multiple versions of Firefox installed, but this seems faulty when installing this package via tarball to a new folder. Ideally, we'd like a way to just tell Firefox to work the old way and make no attempt to support multiple FF versions. We won't ever use it.
We have no way to have 900 users use the Firefox sync account, the data must be stored here and end users would never be able use this feature.
A bit more information, each FF version is installed in a new folder in /u and then a soft link is pointed to the "live" version. The old versions are needed in case we discover a vendor issue or bug in a web page which requires us to check previous versions. This happens quite often, sometimes months after a new release is out.