While working on our own forums in preparation for the coming release of ExpressionEngine 2.1, we discovered a security issue in the Discussion Forum module. The set of circumstances that would expose the issue is extremely rare and cannot even occur in those cases if you are running unmodified stock themes. However, if all of the puzzle pieces are in place, it could allow users to execute certain types of code.
The good news is that we found this ourselves and it probably doesn’t affect you, but the seriousness of the issue if the perfect storm of circumstances does happen to apply to you requires that this update not be understated. We are therefore flagging it as a required update for all users of the Discussion Forum module, both for ExpressionEngine 1.x (Forum version 2.2.0) and 2.x Public Beta (Forum version 3.1.0).
The timing is also fortuitous, as I had just recently made an optimization to the forum search queries. A few months back a misbehaving bot was slamming our forum with searches, and the frequency combined with the complexity of the search ended up crashing MySQL. So instead of waiting for the next feature update to benefit from this optimization, it is available as part of the current update, and should lighten some resource usage for busy forums.
You can download the latest files and documentation in your download section.