Password Change Issue Affects Mac OS X
A Mac OS X bug has surfaced whereby any local user can change that user’s password using a simple Terminal command. This means that anyone who obtains physical or remote (such as via ssh) access to a Mac, and who knows this command – not something that your average user will know – can change [...]
http://blog.intego.com/2011/09/19/password-change-issue-affects-mac-os-x/