Regarding your question how FxV stores its password, I would also recommend you to look at FxV Security and Compliance Filed Guide as a reference. (
In FxV the user account for setup command console "support" and "setup" are Linux users whose password are stored in /etc/shadow. For FxV web console users, their account info including passwords are stored in MySQL table.And passwords are stored in an encoded version. The local MySQL database is also protected through access control (and optionally encrypted on disk).