Issue #3391461: Harden the use of unserialize in InlineBlock via allowed classes

core/modules/layout_builder/src/Plugin/Block/InlineBlock.php

@@ -4,6 +4,7 @@
 
 use Drupal\block_content\Access\RefinableDependentAccessInterface;
 use Drupal\block_content\Access\RefinableDependentAccessTrait;
+use Drupal\Component\Plugin\PluginBase;
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Access\AccessResult;
 use Drupal\Core\Block\BlockBase;
@@ -219,6 +220,20 @@ public function build() {
     return $this->entityTypeManager->getViewBuilder($block->getEntityTypeId())->view($block, $this->configuration['view_mode']);
   }
 
+  /**
+   * Return the unserialized version of the block_serialized configuration.
+   *
+   * @return mixed
+   *   Result of unserialize() function.
+   */
+  protected function getUnserializedBlock(): mixed {
+    $base_class = $this->entityTypeManager->getDefinition('block_content')->getClass();
+    [, $bundle] = explode(PluginBase::DERIVATIVE_SEPARATOR, $this->getPluginId());
+    $bundle_class = $this->entityTypeManager->getStorage('block_content')->getEntityClass($bundle);
+
+    return unserialize($this->configuration['block_serialized'], ['allowed_classes' => [$base_class, $bundle_class]]);
+  }
+
   /**
    * Loads or creates the block content entity of the block.
    *
@@ -228,7 +243,7 @@ public function build() {
   protected function getEntity() {
     if (!isset($this->blockContent)) {
       if (!empty($this->configuration['block_serialized'])) {
-        $this->blockContent = unserialize($this->configuration['block_serialized']);
+        $this->blockContent = $this->getUnserializedBlock();
       }
       elseif (!empty($this->configuration['block_revision_id'])) {
         $entity = $this->entityTypeManager->getStorage('block_content')->loadRevision($this->configuration['block_revision_id']);
@@ -272,7 +287,7 @@ public function saveBlockContent($new_revision = FALSE, $duplicate_block = FALSE
     /** @var \Drupal\block_content\BlockContentInterface $block */
     $block = NULL;
     if (!empty($this->configuration['block_serialized'])) {
-      $block = unserialize($this->configuration['block_serialized']);
+      $block = $this->getUnserializedBlock();
     }
     if ($duplicate_block) {
       if (empty($block) && !empty($this->configuration['block_revision_id'])) {