/usr/share/xul-ext/firetray/modules/ is in xul-ext-firetray 0.5.3~rc1+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xul-ext/firetray/modules/FiretrayHandler.jsm
/usr/share/xul-ext/firetray/modules/FiretrayMessaging.jsm
/usr/share/xul-ext/firetray/modules/FiretrayWindow.jsm
/usr/share/xul-ext/firetray/modules/PrefListener.jsm
/usr/share/xul-ext/firetray/modules/VersionChange.jsm
/usr/share/xul-ext/firetray/modules/commons.js
/usr/share/xul-ext/firetray/modules/ctypes/
/usr/share/xul-ext/firetray/modules/ctypes/ctypes-utils.jsm
/usr/share/xul-ext/firetray/modules/ctypes/ctypesMap.jsm
/usr/share/xul-ext/firetray/modules/ctypes/libfiretray.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/
/usr/share/xul-ext/firetray/modules/ctypes/linux/cairo.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/gdk.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/gio.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/glib.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/gobject.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/gtk.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/libc.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/pango.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/pangocairo.jsm
/usr/share/xul-ext/firetray/modules/ctypes/linux/x11.jsm
/usr/share/xul-ext/firetray/modules/linux/
/usr/share/xul-ext/firetray/modules/linux/FiretrayChat.jsm
/usr/share/xul-ext/firetray/modules/linux/FiretrayChatStatusIcon.jsm
/usr/share/xul-ext/firetray/modules/linux/FiretrayGtkIcons.jsm
/usr/share/xul-ext/firetray/modules/linux/FiretrayPopupMenu.jsm
/usr/share/xul-ext/firetray/modules/linux/FiretrayStatusIcon.jsm
/usr/share/xul-ext/firetray/modules/linux/FiretrayWindow.jsm
/usr/share/xul-ext/firetray/modules/log4moz.js
/usr/share/xul-ext/firetray/modules/logging.jsm