WordPress at a glance
filter is not described

login_form_defaults filter-hook . WP 3.0.0

Filters the default login form output arguments.

Usage

add_filter( 'login_form_defaults', 'filter_function_name_9280' );
function filter_function_name_9280( $defaults ){
	// filter...

	return $defaults;
}
$defaults(array)
An array of default login form arguments.

Where the hook is called

wp_login_form()
login_form_defaults
wp-includes/general-template.php 419
$args = wp_parse_args( $args, apply_filters( 'login_form_defaults', $defaults ) );

Where the hook is used (in WP core)

Does not used.