Index: wp-admin/includes/class-wp-upgrader.php
===================================================================
--- wp-admin/includes/class-wp-upgrader.php	(revision 31788)
+++ wp-admin/includes/class-wp-upgrader.php	(working copy)
@@ -2617,6 +2617,18 @@
 		if ( ! $this->should_update( $type, $item, $context ) )
 			return false;
 
+		/**
+		 * Fires just prior to an auto-update.
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param string $type The type of update being checked: 'core', 'theme', 'plugin', 'translation'.
+		 * @param object $item The update offer.
+		 * @param string $context The filesystem context (a path) against which filesystem
+		 *                        access and status should be checked.
+		 */
+		do_action( "pre_auto_update", $type, $item, $context );
+
 		$upgrader_item = $item;
 		switch ( $type ) {
 			case 'core':