Check the archives. This question has been answered already several times.
Here's an answer from Nick Holland on such a question: http://marc.info/?l=openbsd-misc&m=119931837024703&w=2 BR, Stijn LEFIEUX Morgan wrote:
Hi,i was looking at this page http://www.openbsd.org/pkg-stable.html and would like to know why there is no security fixes for packages after 4.1 release ?Thanks. Comete
