Kimai is an open-source time tracking application. From version 2.32.0 to before version 2.56.0, users with the role System-Admin (ROLE_SYSTE_ADMIN) and the permission upload_invoice_template can upload PDF invoice templates, which can call pdfContext.setOption('associated_files', ...) inside the sandboxed Twig render. This is forwarded to mPDF's SetAssociatedFiles(), whose writer calls file_get_contents($entry['path']) during PDF output and embeds the bytes as a FlateDecode stream in the PDF. Any file readable by the PHP worker is returned to the attacker inside the rendered invoice. This issue has been patched in version 2.56.0.

Affected: Packagist: kimai/kimai

## Summary

Users with the role `System-Admin` (`ROLE_SYSTE_ADMIN`) and the permission `upload_invoice_template` can upload PDF invoice templates, which can call `pdfContext.setOption('associated_files', ...)` inside the sandboxed Twig render.

This is forwarded to mPDF's `SetAssociatedFiles()`, whose writer calls `file_get_contents($entry['path'])` during PDF output and embeds the bytes as a FlateDecode stream in the PDF. Any file readable by the PHP worker is returned to the attacker inside the rendered invoice.

## Root cause

1. `src/Twig/SecurityPolicy/StrictPolicy.php:123-128` explicitly whitelists `PdfContext::setOption()`: ```php if ($obj instanceof PdfContext) { if ($lcm !== 'setoption') { throw ...; } return; } ```

2. `src/Pdf/MPdfConverter.php` keeps `associated_files` in the pass-through allowlist: ```php $allowed = ['mode','format','default_font_size','default_font', ... , 'associated_files','additional_xmp_rdf']; ``` and then forwards it to mPDF: ```php if (array_key_exists('associated_files', $options) && is_array($options['associated_files'])) { $associatedFiles = $options['associated_files']; unset($options['associated_files']); } ... $mpdf->SetAssociatedFiles($associatedFiles); ```

3. mPDF 8.3.1 `MetadataWriter::writeAssociatedFiles()` calls `file_get_contents`, which respects PHP stream wrappers: ```php if (isset($file['path'])) { $fileContent = @file_get_contents($file['…