Where can I find documentation on module updates and security

Well, not being sure exactly what you are looking for there are two top-level sections for both of those:

http://drupal.org/update/modules
http://drupal.org/writing-secure-code

What is it you are looking for, or did you seriously not even look in the handbook?

Lullabot loves you | Be a Ninja, join the Drupal Dojo

http://drupal.org/security-team

-Steven Peck
---------
Test site, always start with a test site.
_{Drupal Best Practices Guide -|- Black Mountain}