Index: wp-admin/includes/class-wp-upgrader.php
===================================================================
--- wp-admin/includes/class-wp-upgrader.php	(revision 28074)
+++ wp-admin/includes/class-wp-upgrader.php	(working copy)
@@ -347,6 +347,23 @@
 		);
 
 		$options = wp_parse_args($options, $defaults);
+		
+		/**
+		 * Filter the package options before running an update. 
+		 * 
+		 * @param array $options {
+		 * 		Options used by the upgrader. 
+		 * 
+		 * 		@type string $package                   Package for update.
+		 * 		@type string $destination               Update location.
+		 * 		@type bool $clear_destination           Clear the destination resource.
+		 * 		@type bool $clear_working               Clear the working resource.
+		 * 		@type bool $abort_if_destination_exists Abort if the Destination directory exists.
+		 *		@type bool $is_multi                    Whether the upgrader is running multiple times.
+		 *		@type array $hook_extra                 Extra hook arguments.
+		 * }
+		 */
+		$options = apply_filters( 'upgrader_package_options', $options );
 		extract($options);
 
 		if ( ! $is_multi ) // call $this->header separately if running multiple times