Legacy browser support
We recommend keeping Firefox up to date so your users have the latest security and performance fixes, but here’s what to do if your users need legacy browser or plugin support.
Web pages that require legacy browsers
Legacy add-ons and plugins are no longer supported in Firefox versions 52 and up, except for the NPAPI Flash plugin.
You can also use Firefox ESR version 52 combined with Windows 32-bit to use other NPAPI plugins like the Java plugin.