I used to hate that Debian always was behind on software versions, but now I use different package sources for the few applications where I really don't want to rely on old software (like browsers), and otherwise doing great with the old stuff :-)
If you're running Firefox on Debian please make sure you manually update it since the package repo's been down for a while. I filed a 'support' ticket first ( https://support.mozilla.org/en-US/questions/1510388 ) since it seemed to be the proper place, but no one seems to look at those.
It's simply a release from Mozilla's Extended Support Release channel, as distinct from the Rapid Release channel that you are apparently using. Not a different project/product.
https://support.mozilla.org/en-US/kb/choosing-firefox-update...