I think alternate way for check RSS System.
For this way using ticket system. Tickets update each week. And user must obtain new RSS link.
Tickets use same way, for example
Then RSS page read ticket. Tickets contain user id and date but do not understandin (Ex:asd787a8d78a7s87d244f) Check ticket date (expired?) and user permission for this forum. If ok only publish XML content.
This way guarantee user will not hack. If somebody learn this RSS link who will access via RSS reader (not forum). And after 1 week, ticket expire. Only user must obtain new RSS link. RSS link automaticly generating when user browse to forum. Each user's RSS link is different. If user dont access to some forum (permission denied) user can not obtain RSS link.
Ticket expire date is last logon time + 7 days
What do you think this way borg ? Any security bug ?