diff --git a/src/Twig/Extension/UtilsExtension.php b/src/Twig/Extension/UtilsExtension.php
index d02bbab..606d37d 100644
--- a/src/Twig/Extension/UtilsExtension.php
+++ b/src/Twig/Extension/UtilsExtension.php
@@ -20,6 +20,7 @@
 
 use Twig\Extension\AbstractExtension;
 use Twig\TwigFilter;
+use function Cake\Core\deprecationWarning;
 
 /**
  * Class UtilsExtension.
@@ -34,8 +35,16 @@ class UtilsExtension extends AbstractExtension
     public function getFilters(): array
     {
         return [
-            new TwigFilter('serialize', 'serialize'),
-            new TwigFilter('unserialize', 'unserialize'),
+            new TwigFilter('serialize', function (string $value): mixed {
+                deprecationWarning('5.0.2', 'Usage of serialize in templates deprecated.');
+
+                return serialize($value);
+            }),
+            new TwigFilter('unserialize', function (string $value): mixed {
+                deprecationWarning('5.0.2', 'unserialize is deprecated. Its usage creates arbitrary object deserialization issues');
+
+                return unserialize($value, ['allowed_classes' => false]);
+            }),
             new TwigFilter('md5', 'md5'),
             new TwigFilter('base64_encode', 'base64_encode'),
             new TwigFilter('base64_decode', 'base64_decode'),
diff --git a/tests/TestCase/Twig/Extension/UtilsExtensionTest.php b/tests/TestCase/Twig/Extension/UtilsExtensionTest.php
new file mode 100644
index 0000000..f9c1784
--- /dev/null
+++ b/tests/TestCase/Twig/Extension/UtilsExtensionTest.php
@@ -0,0 +1,55 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)
+ * Copyright (c) 2014 Cees-Jan Kiewiet
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)
+ * @link          https://cakephp.org CakePHP(tm) Project
+ * @since         1.0.0
+ * @license       https://opensource.org/licenses/mit-license.php MIT License
+ */
+
+namespace Cake\TwigView\Test\TestCase\Twig\Extension;
+
+use Cake\TwigView\Twig\Extension\UtilsExtension;
+use TestApp\GadgetMarker;
+use Twig\Environment;
+use Twig\Loader\ArrayLoader;
+
+class UtilsExtensionTest extends AbstractExtensionTest
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->extension = new UtilsExtension();
+    }
+
+    public function testUnserializePreventObject(): void
+    {
+        $this->skipIf(PHP_VERSION_ID < 80300, 'Requires PHP8.3 or higher');
+
+        $twig = new Environment(new ArrayLoader([
+            // {% set %} so we exercise the filter without stringifying the result.
+            'object' => '{% set _ = payload|unserialize %}(rendered)',
+            'array' => '{{ (payload|unserialize)["role"] }}',
+        ]));
+        $twig->addExtension(new UtilsExtension());
+
+        // 1) Object payload: does a gadget's magic method run?
+        GadgetMarker::$woken = false;
+        $this->deprecated(function () use ($twig): void {
+            $twig->render('object', ['payload' => serialize(new GadgetMarker())]);
+            $this->assertFalse(GadgetMarker::$woken, 'Should not have modified GadgetMarker');
+
+            $out = $twig->render('array', ['payload' => serialize(['role' => 'editor'])]);
+            $this->assertStringContainsString('editor', $out);
+        });
+    }
+}
diff --git a/tests/test_app/src/GadgetMarker.php b/tests/test_app/src/GadgetMarker.php
new file mode 100644
index 0000000..a159879
--- /dev/null
+++ b/tests/test_app/src/GadgetMarker.php
@@ -0,0 +1,15 @@
+<?php
+declare(strict_types=1);
+
+namespace TestApp;
+
+class GadgetMarker
+{
+    public static bool $woken = false;
+
+    public function __wakeup(): void
+    {
+        self::$woken = true;
+        echo "  [!] GadgetMarker::__wakeup fired during unserialize (object injection)\n";
+    }
+}