From 2731d292497d35c3605316f02dba900abf65e626 Mon Sep 17 00:00:00 2001
From: Maximilian Graf Schimmelmann <max@schimmelmann.org>
Date: Sat, 16 May 2026 10:58:07 +0200
Subject: [PATCH] Fix Invalid UTF-8 character error for potential malformed
 user input.

---
 composer.json                                     | 3 ++-
 src/Field/Configurator/CollectionConfigurator.php | 7 ++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/composer.json b/composer.json
index f251628035..b62471bb3f 100644
--- a/composer.json
+++ b/composer.json
@@ -39,7 +39,8 @@
         "symfony/validator": "^5.4|^6.0|^7.0|^8.0",
         "twig/extra-bundle": "^3.17",
         "twig/html-extra": "^3.17",
-        "twig/twig": "^3.20"
+        "twig/twig": "^3.20",
+        "ext-mbstring": "*"
     },
     "require-dev": {
         "doctrine/doctrine-fixtures-bundle": "^3.4|3.5.x-dev|^4.0",
diff --git a/src/Field/Configurator/CollectionConfigurator.php b/src/Field/Configurator/CollectionConfigurator.php
index 92dd6dfd61..28fe63db23 100644
--- a/src/Field/Configurator/CollectionConfigurator.php
+++ b/src/Field/Configurator/CollectionConfigurator.php
@@ -106,7 +106,12 @@ private function formatCollection(FieldDto $field, AdminContext $context): int|s
                 return $this->countNumElements($field->getValue());
             }
 
-            $collectionItemsAsText[] = (string) $item;
+            $itemString = (string) $item;
+            if (!mb_check_encoding($itemString, 'UTF-8')) {
+                $itemString = mb_convert_encoding($itemString, 'UTF-8', 'UTF-8');
+            }
+
+            $collectionItemsAsText[] = $itemString;
         }
 
         $isDetailAction = Action::DETAIL === $context->getCrud()->getCurrentAction();