@phpdeveloper.org
According to this forum post on the NeoSmart message boards, there's a new "0-day vulnerability" that they've discovered in the phpBB message board system.
Our research team has discovered a new (aka 0-day) vulnerability in phpBB, that affects all existing versions (including the Olympus CVS as of May 18th, 2006).
This phpBB security vulnerability has been scaled at a threat level of 6/10; allowing normal members access to privileged and restricted-access content on a phpBB forum. The bug lies in the email notification system and can be used to track comments made on any hidden posts that were once user accessible.
Since this bug has just broken today, there's no response from phpBB as of yet with a patch, but expect it soon if this issue is as important as the post mentions.