Craft CMS versions 5.5.0 through 5.9.13 contain a remote code execution vulnerability in the FieldsController::actionRenderCardPreview() method. This flaw allows an authenticated admin user to inject Yii2 event handlers via the fieldLayoutConfig POST parameter, leading to arbitrary PHP code execution and potential disclosure of sensitive information such as environment variables and security keys. The vulnerability is fixed in version 5.9.14.