diff --git a/src/wp-includes/blocks/rss.php b/src/wp-includes/blocks/rss.php
index 0315cfc013..07ddb3d007 100644
--- a/src/wp-includes/blocks/rss.php
+++ b/src/wp-includes/blocks/rss.php
@@ -92,7 +92,7 @@ function render_block_core_rss( $attributes ) {
 		$class .= ' ' . $attributes['className'];
 	}
 
-	return "<ul class='{$class}'>{$list_items}</ul>";
+	return sprintf( "<ul class='%s'>%s</ul>", esc_attr( $class ), $list_items );
 }
 
 /**
diff --git a/src/wp-includes/blocks/search.php b/src/wp-includes/blocks/search.php
index 5face0b929..a140caf0e0 100644
--- a/src/wp-includes/blocks/search.php
+++ b/src/wp-includes/blocks/search.php
@@ -57,7 +57,7 @@ function render_block_core_search( $attributes ) {
 
 	return sprintf(
 		'<form class="%s" role="search" method="get" action="%s">%s</form>',
-		$class,
+		esc_attr( $class ),
 		esc_url( home_url( '/' ) ),
 		$label_markup . $input_markup . $button_markup
 	);