Comment # 3 on bug 1053314 from Theodore Beare

Apologies for continuing this in the wrong place, but I was unable to subscribe
to the factory mailing lists and could therefore not respond to the discussion
there.  However, I thought it was worthwhile pointing out that Firefox profiles
for version 55+ can be "refreshed" to work with Firefox 52 via about:support
(though I have not tested this personally).  Presumably this would also work
for certain other "old" versions of Firefox.

See:

https://bugzilla.mozilla.org/show_bug.cgi?id=1357428#c2