Comment 3 for bug 1113353

Bug still exists in WebApps: libunity 2.4.1 and is about unity-webapps-service.c where i found function:

/** //line 955
 *
 * @return command line format, have to be freed
 */
static char *
get_browser_command_line_format (const gchar *homepage)
{
  static const char * URI_SCHEME_HTTP = "http";

  GAppInfo * info = g_app_info_get_default_for_uri_scheme (URI_SCHEME_HTTP);
  g_return_val_if_fail (NULL != info, NULL);

  const char * exe_name = g_app_info_get_executable (info);
  g_return_val_if_fail (NULL != exe_name, NULL);

  if (g_str_has_suffix (exe_name, "firefox"))
    {
      /* gchar *profile_path = _firefox_get_profile_for_app (homepage);

      if (profile_path)
 {
   return g_strdup_printf ("%s --chromeless -no-remote -profile %s '%%s'", exe_name, profile_path);
   }*/
      return g_strdup_printf ("%s --new-window '%%s'", exe_name);
    }
  return g_strdup_printf ("%s --chromeless --new-window '%%s'", exe_name);
} //line 981

I do not know why this option is set permanently to open new window, because we can choose in browser options how to open website.