Liz is right; there was never an official release of Firefox labelled 47 on the ESR channel. The final 'update' of 45esr went as far as 45.9.0.
What you
may have there is what I term a 'Frankenstein' build. Certain individuals were known to have downloaded a main-line release, switched to the ESR channel
before a channel 'update' came through, then re-mastered/re-compiled the thing and built their own .exe packages from it. Don't ask me why; I never
could figure out WHY some folks do the things they do!
This could then have very well found its way into the repos of one of the numerous third-party download sites. Do you happen to remember exactly
where you got this thing from?
Mike.