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. Stefan Esser will release details of the complete attack shortly. The attack is difficult to accomplish, but its mere possibility means we recommend upgrading to 2.6.2.

You can download WordPress 2.6.2 here.