Description of problem:
  URL-open from xchat fails to open in Firefox 36.0 because Firefox removed the
"-remote" option, apparently making that the default behaviour.  Unfortunately
they destroyed back-compatability by not just ignoring it; you now get a new
Firefox window with your configured start page.
  This will presumably trip any application using the exo helper route.
Workaround is to configure a custom browser in Preferred Applications, with
an exec-string "firefox %s"

Version-Release number of selected component (if applicable):
  exo-0.10.2-8.fc21.x86_64
  firefox-36.0-1.fc21.x86_64
  xchat-2.8.8-26.fc21.x86_64

How reproducible:
  100%

Steps to Reproduce:
1. Start firefox
2. In xchat, ctrl-click a URL

Actual results:
  New firefox window, with configured start content (if any)

Expected results:
  Requested URL opened in new tab in existing firefox window

Additional info: