Ticket #31896: 31896.2.diff

src/wp-includes/class-wp-customize-control.php

@@ -1242 +1242 @@
          * @access public
          */
         public function content_template() {
-                $preview_url = site_url( add_query_arg( 'theme', '{{ data.theme.id }}' ) );
+                $current_url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] );
+                $preview_url = add_query_arg( 'theme', '{{ data.theme.id }}', $current_url );
                 ?>
                 <div class="theme" tabindex="0" data-preview-url="<?php echo esc_attr( $preview_url ); ?>" aria-describedby="{{ data.theme.id }}-action {{ data.theme.id }}-name">
                         <# if ( data.theme.screenshot[0] ) { #>