This is cPanel Hooks v2.0 for cPanel 11.25.0

Hooks only work for Api2 functions, and a few Api1 functions that have been
spruced up on the backend.  One of those is Passwd::change_passwd

Please see cpanel/hooks/passwd/change_password.example.
If you just want a quick and dirty test copy it to
cpanel/hooks/passwd/change_password. Please note that all hooks run as root.

In order for cpanel to see new hooks you must now run:
/usr/local/cpanel/bin/register_hooks

Custom Event handlers allow you to trap, and/or prevent default actions from
happening. If a custom event handler returns false, execution of the event
stops. These work for api1, and api2. Note that api1 calls provide a lot less
information to the Event Handler.

You make also want to write a Custom Event Handler.
see cpanel/Cpanel/EventHandler.pm
You can place your customer EventHandler in:
/usr/local/cpanel/Cpanel/CustomEventHandler.pm
