jar protocol, that allows to directly link to a file in ZIP archives, is no longer available from Web content due to security concerns. No other browsers support this Java archive protocol so far.
To enable the
jar support for any reason on Firefox 45 and later, flip the
network.jar.block-remote-files preference value to
false. Otherwise, loading the
jar protocol will lead to the
Update: Since IBM iNotes is broken due to this change, the
jar protocol support has been temporarily restored with Firefox 45.0.1. On Firefox Nightly and Developer Edition, the
network.jar.block-remote-files preference will remain
Update 2: The iNotes issue has been fixed with IBM Notes/Domino 9.0.1 Fix pack 6 released in May 2016.
Update 3: Given that iNotes no longer relies on the
jar support, Mozilla is planning to make it disabled again. Firefox 52 Extended Support Release (ESR) for organizations won’t be affected by this change, so the older versions of iNotes, if any, can still be used on the ESR until May 2018.
Update 4: The JAR support has been disabled again with Firefox 55.