Ticket #57635: 57635.2.patch

wp-includes/user.php

@@ -2122 +2122 @@
         // user_login must be between 0 and 60 characters.
         if ( empty( $user_login ) ) {
                 return new WP_Error( 'empty_user_login', __( 'Cannot create a user with an empty login name.' ) );
+        } if( empty(sanitize_title( $user_login ))){
+                return new WP_Error( 'invalid_user_login', __( 'Please enter valid login name.' ) );
         } elseif ( mb_strlen( $user_login ) > 60 ) {
                 return new WP_Error( 'user_login_too_long', __( 'Username may not be longer than 60 characters.' ) );
         }