mosquitto/www/posts/2012/09/updating-password-files.md

Mosquitto 1.0 introduced the use of password files with hashed passwords but had no way to convert from the old plain text password files. This feature will be available in version 1.1 but if it is important to you then you can already get the updated code for the mosquitto_passwd utility at https://bitbucket.org/oojah/mosquitto/src/3b8ef11cf687