Firefox has dropped NPAPI plug support (except flash) in ver 52. Gentoo is left with no browser to run java plugins. Please provide Firefox ESR (via a use flag or as a separate ebuild) that allows running java plugins.
workaround: there is still www-client/firefox-51.0.1::gentoo in the portage tree, where it might still work.
Confirmed: www-client/firefox-51.0.1::gentoo does work with Oracle JRE plugin.
Please re-add firefox-bin-51 as a workaround for people who need Java support and don't want to build firefox from source.
Firefox ESR is currently at 45.8 and will also be 52.1 once 45.8 is no longer stable. If you notice, these are the "stable" (non-~arch) keyworded versions. We will not be providing a firefox-bin-52.0 ESR as the stable/~arch combination sinply doesn't work in that case. If you insist on using ~arch firefox-bin and want to continue to have non-flash plugin support, you can hack your about:config to include the key 'plugin.load_flash_only' with value 'false'. However I would highly recommend relying on 45.8 or building from source with USE="nsplugin" instead at this time. OR, accepting the pack of plugin support and using JavaWebStart to paunch your applets.
s/pack/lack/ s/paunch/launch/, apologies for the typos.
I built firefox-51 from source now, but on a later 'emerge --sync' I notice that now firefox-51 is also removed. While I understand that you cannot make 51 stable, I don't understand why 45, 51 and 52 can not coexist in portage, 51 remaining ~arch. Can you clarify?