Shopware 6.7.13.1: Securing Your Store by Adapting to the `template_from_string` Removal

Shopware 6.7.13.1: Securing Your Store by Adapting to the `template_from_string` Removal

In the fast-evolving world of e-commerce, security is paramount. Shopware, a leading platform, consistently releases updates to enhance functionality and, critically, to fortify its defenses against emerging threats. A recent discussion in the Shopware forum highlighted a significant change introduced with Shopware version 6.7.13.1: the deprecation or apparent removal of the template_from_string Twig function. This isn't just a minor technical adjustment; it's a proactive and essential security measure that demands attention from every Shopware developer and store owner.

At Migrate My Store, we understand that such changes, while vital for security, can pose challenges for existing custom implementations. Our goal is to guide you through understanding this update and adapting your store to maintain both functionality and robust security.

The `template_from_string` Function: A Powerful Tool with Hidden Risks

Before its removal, the template_from_string Twig function offered developers immense flexibility. It allowed for the dynamic rendering of Twig snippets directly from strings, which could be stored in various places like product descriptions, custom fields, or configuration settings. This was particularly useful for:

• Displaying dynamic, context-sensitive messages.
• Integrating translated content directly into templates.
• Allowing merchants to embed simple logic or variables within content areas without direct code access.

As user klogges described in the forum, their setup relied on this functionality to render dynamic content from custom fields. They used constructs like:

{{ include(template_from_string(product.customFields.product_important_infos)) }}

Where product.customFields.product_important_infos itself might contain a Twig snippet such as {{ "some.translation.key" | trans | raw }}. This approach, while convenient, inadvertently opened a door to a severe security vulnerability.

Unveiling the Threat: CVE-2026-46634 and Server-Side Template Injection (SSTI)

The reason behind the removal of template_from_string lies in a critical vulnerability identified in Symfony, the underlying framework for Shopware. User Max_Shop promptly pointed to CVE-2026-46634, detailed in a Symfony blog post. This CVE revealed that template_from_string() could escape a SourcePolicy-driven sandbox via a synthesized template name, leading to a Server-Side Template Injection (SSTI) vulnerability.

What is SSTI? Server-Side Template Injection occurs when an attacker can inject malicious template code into a web application, which is then executed by the server-side template engine. In the context of template_from_string, if an attacker could manipulate the input string being passed to this function (e.g., through a compromised custom field or an insecure form submission), they could potentially execute arbitrary code on your server. The implications are severe:

• Data Breaches: Access to sensitive customer or business data.
• Site Defacement: Altering your storefront with malicious content.
• Remote Code Execution (RCE): Gaining full control over your server, leading to complete system compromise.

Shopware, inheriting its core components from Symfony, was directly impacted by this vulnerability. The risk was simply too high to maintain the function in its previous form.

Shopware's Decisive Action: Prioritizing Security

The removal or significant restriction of template_from_string in Shopware 6.7.13.1 is a direct and necessary response to CVE-2026-46634. By eliminating this specific attack vector, Shopware ensures that even if untrusted input were to reach a template rendering context, it would not be interpreted as executable Twig code. This move underscores Shopware's commitment to providing a secure e-commerce platform, even if it means breaking compatibility for certain legacy implementations.

Adapting Your Store: Secure Alternatives and Best Practices

If your Shopware store relied on template_from_string, it's crucial to audit your codebase and implement secure alternatives. Here’s how to approach the migration:

1. Audit Your Codebase

Thoroughly search your custom themes, plugins, and overridden templates for any occurrences of template_from_string. Identify where and how dynamic content was being rendered.

2. Implement Custom Twig Functions for Safe Data Processing

Inspired by klogges' solution, the recommended approach is to create your own custom Twig function. The key difference is that this new function should not interpret its input as executable Twig code. Instead, it should safely retrieve, process, and output data.

For example, if you previously stored a Twig snippet like {{ "some.translation.key" | trans | raw }} in a custom field, you should now store only the translation key (e.g., some.translation.key) or the final translated text itself. Your custom Twig function would then:

• Retrieve the custom field value.
• Use Shopware's TranslatorInterface to translate the key (if applicable).
• Crucially, sanitize the output to prevent any HTML or script injection before rendering.

Here’s a conceptual example of how such a custom Twig function might be structured (implementation details would vary based on your specific needs):

// In your custom Twig Extension (e.g., MyCustomTheme/src/Core/Framework/Twig/Extension/SafeContentExtension.php)

namespace MyCustomTheme\Core\Framework\Twig\Extension;

use Shopware\Core\Framework\Adapter\Twig\Extension\PhpFunctionExtension;
use Symfony\Contracts\Translation\TranslatorInterface;
use Twig\Extension\AbstractExtension;
use Twig\TwigFunction;

class SafeContentExtension extends AbstractExtension
{
    private TranslatorInterface $translator;

    public function __construct(TranslatorInterface $translator)
    {
        $this->translator = $translator;
    }

    public function getFunctions(): array
    {
        return [
            // This function safely retrieves and translates content, without parsing it as Twig.
            new TwigFunction('render_safe_custom_field', [$this, 'renderSafeCustomField'], ['is_safe' => ['html']]),
        ];
    }

    public function renderSafeCustomField(string $customFieldKey, array $c string
    {
        // Example: Safely retrieve content from a product's custom fields
        // Ensure 'product' is available in the Twig context if you're using it.
        $value = $context['product']['customFields'][$customFieldKey] ?? '';

        // Translate the value if it's a translation key
        $translatedValue = $this->translator->trans($value);

        // IMPORTANT: Sanitize the output to prevent XSS. 
        // Depending on your needs, you might use a dedicated HTML purifier library.
        // For simple text, htmlspecialchars() is a good start.
        return htmlspecialchars($translatedValue, ENT_QUOTES | ENT_HTML5, 'UTF-8');
    }
}

And in your Twig template, you would then use it like:

{{ render_safe_custom_field('product_important_infos', { 'product': product }) }}

This ensures that the content is treated as data, not as executable code.

3. Leverage Shopware's Content Elements and Blocks

For rich, dynamic content areas, consider using Shopware's built-in CMS capabilities. Content elements and blocks provide a secure way for merchants to create complex layouts and insert various types of content without directly interacting with Twig code.

4. Strict Input Validation and Sanitization

Always validate and sanitize any user-generated or merchant-entered content, especially for custom fields. This should happen at the point of input (e.g., when saving data in the administration panel) to prevent malicious code from ever being stored in your database.

The Broader Message: Prioritizing Security in E-commerce

The removal of template_from_string is a stark reminder of the constant battle against cyber threats. For e-commerce businesses, security isn't just a technical detail; it's fundamental to customer trust, data integrity, and business continuity. Regularly updating your Shopware instance, auditing custom code, and understanding the underlying security advisories are non-negotiable practices.

At Migrate My Store, we specialize in ensuring your Shopware environment is not only performant but also secure. Whether you're upgrading to the latest Shopware version or need assistance in auditing and refactoring your custom code for enhanced security, our experts are here to help you navigate these critical changes seamlessly.

Stay informed, stay updated, and keep your Shopware store secure. This proactive approach will safeguard your business and your customers in the long run.