According to http://www.phpbb.com/phpBB/viewtopic.php?f=14&t=240513 there is a very critical Bug in phpBB.
All old versions (/ebuilds) should be upgraded as soon as possibly.
Steps to Reproduce:
phpBB 2.0.10 insecure
phpBB 2.0.11 secure
*** This bug has been marked as a duplicate of 71681 ***