Index: src/wp-includes/user.php
===================================================================
--- src/wp-includes/user.php	(revision 33680)
+++ src/wp-includes/user.php	(working copy)
@@ -2063,6 +2063,32 @@
 
 	$user = new WP_User( $user_id );
 
+	/**
+ 	 * Filter a user's meta values and keys before the user is created or updated.
+ 	 *
+ 	 * Does not include contact methods. These are added using `wp_get_user_contact_methods( $user )`.
+ 	 *
+ 	 * @since 4.4.0
+ 	 *
+ 	 * @param array $meta {
+ 	 *     Default meta values and keys for the user.
+ 	 *
+ 	 *     @type string   $nickname             The user's nickname. Default is the the user's username.
+	 *     @type string   $first_name           The user's first name.
+	 *     @type string   $last_name            The user's last name.
+	 *     @type string   $description          The user's description.
+	 *     @type bool     $rich_editing         Whether to enable the rich-editor for the user. False if not empty.
+	 *     @type bool     $comment_shortcuts    Whether to enable keyboard shortcuts for the user. Default false.
+	 *     @type string   $admin_color          The color scheme for a user's admin screen. Default 'fresh'.
+	 *     @type int|bool $use_ssl              Whether to force SSL on the user's admin area. 0|false if SSL is
+	 *                                          not forced.
+	 *     @type bool     $show_admin_bar_front Whether to show the admin bar on the front end for the user.
+	 *                                          Default true.
+ 	 * }
+ 	 * @param WP_User $user User object.
+ 	 */
+	$meta = (array) apply_filters( 'insert_user_meta', $meta, $user ); 
+	
 	// Update user meta.
 	foreach ( $meta as $key => $value ) {
 		update_user_meta( $user_id, $key, $value );