To see if you are using an ESR release, check the Firefox menu item (Help - About) and looking for the "ESR" identifier.
Mozilla maintains Firefox ESR Releases for approximately one year.
Also it now tells me Firefox is an older version and invites me to download an updated version.
Am I safe to do so and will this solve my plug in problem.
In 2012, Adobe announced they would no longer developing the NPAPI plug-in for Linux, but they would continue developing the Pepper-based Flash plug-in used in Chrome. Other browsers on all operating systems — Firefox, Safari, and even Chrome until recently — use the NPAPI framework.
NPAPI was originally developed for Netscape — NPAPI stands for “Netscape Plugin Application Programming Interface.” It became the standard plug-in architecture that all non-Internet-Explorer browsers used. In 2013, Google announced their intention to remove NPAPI support from Chrome because “NPAPI’s 90s-era architecture has become a leading cause of hangs, crashes, security incidents, and code complexity.” They’ve replaced NPAPI with Pepper, also known as PPAPI.
On Linux, the NPAPI plug-in is stuck at 11.2 while the current version of Flash is 14.