Content-hub DBUS API doesn't prevent confined apps from passing paths to files without access

Content Hub before version 0.0+15.04.20150331-0ubuntu1.0 DBUS API only requires a file path for a content item, it doesn't actually require the confined app have access to the file to create a transfer. This could allow a malicious application using the DBUS API to export file:///etc/passwd which would then send a copy of that file to another app.