The attachments on forum postings are visible only to registered users who are logged in. I'm not sure this is necessary. Why not make the attachments available to everybody?
If that's not considered secure enough, we could do this: When a message is requested, have the forum engine check it for attachments. If there are none, no problem. If there are, check if the client is logged in. If so, present the attachments as usual; if not, print one line saying something like, "This message has attachments. To see them, please [link]login[/link] or [link]register.[/link]"
(Yesterday I was scanning the forums for a particular attachment, without logging in. I couldn't find them, and it took a few minutes to guess why they had all become invisible.)
Thanks, and best regards to Team TC.