The BA Book Everything plugin for WordPress is vulnerable to arbitrary password reset in all versions up to, and including, 1.6.20. This is due to the reset_user_password() function not verifying a user's identity prior to setting a password. This makes it possible for unauthenticated attackers to reset any user's passwords, including administrators. It's important to note that the attacker will not have access to the generated password, therefore, privilege escalation is not possible.
When setting a new password for a user, the product does not require knowledge of the original password, or using another form of authentication.