Stefan Esser recently warned developers of the dangers of SQL Column Truncation and the weakness of mt_rand(). With his help we worked around these problems and are now releasing WordPress 2.6.2. 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.
Other PHP apps are susceptible to this class of attack. To protect all of your apps, grab the latest version of Suhosin. If you’ve already updated Suhosin, your existing WordPress install is already protected from the full exploit. You should still upgrade to 2.6.2 if you allow open user registration so as to prevent the possibility of passwords being randomized.
2.6.2 also contains a handful of bug fixes. Check out the full changeset and list of changed files.