Anyway back to Oracle security:-
Alex Kornbrust came over to the UKOUG in Birmingham in November 2006 to talk about "Oracle security and Hacking and hardening Oracle Express Edition" in particular. This is a great presentation talking about the security issues in the Oracle XE free version. Alex starts by discussing the architecture and the patch policy (what patch policy?) and then goes on to demonstrate how to hack XE and APEX. Great paper, well worth reading.