• I have tested the latest master version from http://builds.jabref.org/master/ and the problem persists
  JabRef 5.0-dev--snapshot--2018-08-24--master--f43b9c7e8
  Windows 7 6.1 amd64
  Java 1.8.0_181

Steps to reproduce:

1. I tried JabFox from Firefox Quantum 61.0.2. (64Bit)
2. the files where correctly placed and the

`REG ADD "HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla\NativeMessagingHosts\org.jabref.jabref" /ve /d "C:\Program Files\JabRef5\jabref.json" /f

C:\Windows\system32>REG ADD "HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla\NativeMessagingHosts\org.jabref.jabref" /ve /d "C:\Program Files\JabRef5\jabref.json" /f
Der Vorgang wurde erfolgreich beendet....`

was correctly executed.
3. Pressing the Jabfox icon on the page of on https://doi.org/10.1016/B978-0-12-385095-9.00175-5
resulted in some action but the JabRef import window never opened, not even in the background.

It appears that Jabfox is not working with 5.0 dev.