WordPress at a glance
filter is not described

allow_major_auto_core_updates filter-hook . WP 3.7.0

Filters whether to enable major automatic core updates.

Usage

add_filter( 'allow_major_auto_core_updates', 'filter_function_name_9595' );
function filter_function_name_9595( $upgrade_major ){
	// filter...

	return $upgrade_major;
}
$upgrade_major(true/false)
Whether to enable major automatic core updates.

Where the hook is called

Core_Upgrader::should_update_to_version()
wp-admin/includes/class-core-upgrader.php 327
return apply_filters( 'allow_major_auto_core_updates', $upgrade_major );

Where the hook is used (in WP core)

Does not used.