Ticket #20176: ms-functions.diff

ms-functions.php

@@ -437 +437 @@
         $orig_username = $user_name;
         $user_name = preg_replace( '/\s+/', '', sanitize_user( $user_name, true ) );
         $maybe = array();
-        preg_match( '/[a-z0-9]+/', $user_name, $maybe );
+        preg_match( apply_filters( 'wpmu_username_restriction', '/[a-z0-9]+/' ), $user_name, $maybe );
 
         if ( $user_name != $orig_username || $user_name != $maybe[0] ) {
                 $errors->add( 'user_name', __( 'Only lowercase letters (a-z) and numbers are allowed.' ) );