diff --git a/wp-admin/includes/dashboard.php b/wp-admin/includes/dashboard.php
index 2aeaa24e46..f4bda1a30c 100644
--- a/wp-admin/includes/dashboard.php
+++ b/wp-admin/includes/dashboard.php
@@ -1683,7 +1683,7 @@ function wp_dashboard_quota() {
 				__( 'Manage Uploads' )
 			);
 			?>
-		</li><li class="storage-count <?php echo $used_class; ?>">
+		</li><li class="storage-count <?php echo esc_attr( $used_class ); ?>">
 			<?php
 			$text = sprintf(
 				/* translators: 1: Number of megabytes, 2: Percentage. */