WordPress at a glance
action is not described

wp_maybe_auto_update action-hook . WP 1.0

Trigger background updates if running non-interactively, and we weren't called from the update handler.

Usage

add_action( 'wp_maybe_auto_update', 'action_function_name_5403' );
function action_function_name_5403(){
	// action...
}

Where the hook is called

wp_version_check()
wp-includes/update.php 207
do_action( 'wp_maybe_auto_update' );

Where the hook is used (in WP core)

wp-includes/update.php 760
add_action( 'wp_maybe_auto_update', 'wp_maybe_auto_update' );