Nope, quite a range of forum softwares are affected. The softwares I use for forums are:
1. SMF – Simple Machines Forum (Affected)
2. Snitz (May be Affected, or might be some other automated bot)
3. vBulletin (not yet affected)
Here is a snippet from the website:
Software is able to work with lots of different types of forums and guestbooks: phpBB and PHP-Nuke with any modifications, yaBB, VBulletin, Invision Power Board, IconBoard, UltimateBB, exBB, phorum.org, wiki, different types of bulletin boards and even custom-written code.
Version 4.0 is now in beta and that one, apparently, can use more boards – I am sure SMF is one of them. You would have to do your own research to see what stops it. All I know is that I have been affected and I am fairly certain this is the culprit. It’s quite annoying.