diff --git a/test/index.php b/test/index.php
index f6293fb..824e08c 100644
--- a/test/index.php
+++ b/test/index.php
@@ -1,5 +1,13 @@
 <?php
+declare(strict_types=1);
 
-echo htmlspecialchars($_GET["test"], ENT_QUOTES, 'UTF-8');
+// Validate input exists
+if (!isset($_GET['test'])) {
+    die('Invalid input');
+}
+
+// Convert to string and sanitize
+$input = (string)$_GET['test'];
+echo htmlspecialchars($input, ENT_QUOTES | ENT_HTML5, 'UTF-8', true);
 
 ?>