WordPress at a glance
filter is not described

auto_update_(type) filter-hook . WP 3.7.0

Filters whether to automatically update core, a plugin, a theme, or a language.

The dynamic portion of the hook name, $type, refers to the type of update being checked. Can be 'core', 'theme', 'plugin', or 'translation'.

Generally speaking, plugins, themes, and major core versions are not updated by default, while translations and minor and development versions for core are updated by default.

See the {@'allow_dev_auto_core_updates', {@see 'allow_minor_auto_core_updates'}, and 'allow_major_auto_core_updates' filters for a more straightforward way to adjust core updates.

Usage

add_filter( 'auto_update_(type)', 'filter_function_name_5270', 10, 2 );
function filter_function_name_5270( $update, $item ){
	// filter...

	return $update;
}
$update(true/false)
Whether to update.
$item(object)
The update offer.

Where the hook is called

WP_Automatic_Updater::should_update()
wp-admin/includes/class-wp-automatic-updater.php 175
$update = apply_filters( "auto_update_{$type}", $update, $item );

Where the hook is used (in WP core)

Does not used.