Index: src/wp-admin/includes/file.php
===================================================================
--- src/wp-admin/includes/file.php	(revisione 39941)
+++ src/wp-admin/includes/file.php	(copia locale)
@@ -263,6 +263,15 @@
 	 */
 	$file = apply_filters( "{$action}_prefilter", $file );
 
+	/**
+	 * Filters the ovverride action for a file before it is uploaded to WordPress.
+	 *
+	 * The dynamic portion of the hook name, `$action`, refers to the post action.
+	 *
+	 * @param array $file An array of overrides actions.
+	 */
+	$overrides = apply_filters( "{$action}_overrides", $overrides );
+
 	// You may define your own function and pass the name in $overrides['upload_error_handler']
 	$upload_error_handler = 'wp_handle_upload_error';
 	if ( isset( $overrides['upload_error_handler'] ) ) {