FireFox 45.0.2 ESR is the latest ESR release. We currently use the previous ESR release (38). We current plan of record is to upgrade to the next ESR as part of the next MongoDB release (3.4)

It is available here: https://ftp.mozilla.org/pub/firefox/releases/45.0.1esr/source/

The work involved with this will be non-trivial as compared to other third-party packages as spider monkey is not available as a separate source distribution. First it must be extracted from firefox sources, and then our source must be updated to reflect API changes (like AutoIdArray being removed or OOM simulation methods being required in jscustomallocator.h.)

In addition, we have config files for 12 architecture & platform pairs for MozJS 38. This means we need to migrate 9 of them forward to support 64-bit platforms now that 32-bit is disabled.