The good people over at WordPress released WordPress 2.6.2 today. And unlike the previous 2.6.1 release, this release is a mandatory release, to fix a loophole which occurs if your blog has registrations open.
From the horse’s mouth:
If you allow open registration on your blog, you should definitely upgrade. With open registration enabled, it is possible in WordPress versions 2.6.1 and earlier to craft a username such that it will allow resetting another user’s password to a randomly generated password. The randomly generated password is not disclosed to the attacker, so this problem by itself is annoying but not a security exploit. However, this attack coupled with a weakness in the random number seeding in mt_rand() could be used to predict the randomly generated password.
Certainly seems a very important reason to update to 2.6.2. And if you find the process of upgrading WordPress blog a pain, here’s an effortless way of doing it.