php-fusion 4.x vuln

[<thegreatone2176@xxxxxxxxx>]

TheGreatOne2176, Reapercore

I have a found an error in php-fusion 4.x where you can view any thread on the 
forum.

In fusion_forum/viewthread.php the $_GET variables arent properly checked or 
queried making it possible to view all threads. The example I tested was

fusion_forum/viewthread.php?forum_id=10000&forum_cat=100000&thread_id=2

forum_id and forum_cat are not valid id's making the script skip them entirely. 
 So the error comes in since each thread is assigned a certain integer 
(thread_id for this script) and since the category checks were being skipped, I 
could just browse the forum by picking a thread_id. I went number by number and 
could view all of the threads in the protected forums.