A vulnerability has been discovered in all 3.x releases up to 3.14 that allows malicious people to send email through your blog. You should upgrade to 3.15 ASAP!

If you want to do a very quick update from 3.14 (don't do this on any other version!) all you need to upload are the following: doc, lib/MT/Util.pm, lib/MT/Mail.pm and lib/MT.pm

Below is just some information for my own use, a simple upgrade is impossible on my blog without wrecking some of my changed files.

Creative Commons Update
lib/MT/Util.pm
php/lib/cc_lib.php

QuickTags
mt-static/mt.js

Search
search_templates/default.tmpl