A plugin to authenticate users migrated from Joomla/Mambo to WordPress.
Joomla encrypted passwords should be stored in user meta key "joomlapass". When user is authenticated first time after migration password provided by user is encrypted by "joomla way" and compared with value in "joomlapass" meta key. If password is correct WP user is udated - password encrypted by "wordpress way" is stored to "user_pass" field. Then user can be authenticated by standart wordpress authentication plugin. Meta key "joomlapass" is renamed to "joomlapassbak" to avoid repeatedly updating WP password.