Filters the HTML output for the protected post password form.
Description
If modifying the password field, please note that the core database schema limits the password field to 20 characters regardless of the value of the size attribute in the form input.
Parameters
$output
string- The password form HTML output.
$post
WP_Post- Post object.
Source
return apply_filters( 'the_password_form', $output, $post );
This is a working example and 9999 is the priority and you can adjust accordingly.