FacturaScripts is an open source accounting and invoicing software. In 2025.81 and earlier, an authenticated unrestricted file upload vulnerability exists in FacturaScripts' product image upload functionality. An attacker with valid credentials can upload a PHP file disguised as a GIF image (using a GIF89a header), bypassing MIME type validation. The file is stored with its original extension, including executable extensions such as .php. The vulnerability exists the addImageAction() method of Core/Lib/ExtendedController/ProductImagesTrait.php.

Affected: Packagist: facturascripts/facturascripts

# CVE-2026-42879 - FacturaScripts - Authenticated Unrestricted File Upload via MIME Type Bypass ## Summary An authenticated unrestricted file upload vulnerability exists in FacturaScripts' product image upload functionality. An attacker with valid credentials can upload a PHP file disguised as a GIF image (using a GIF89a header), bypassing MIME type validation. The file is stored with its original extension, including executable extensions such as .php. --- ## Details The vulnerability exists in: `Core/Lib/ExtendedController/ProductImagesTrait.php` Specifically in the `addImageAction()` method. ### Vulnerable Code ```php if (false === strpos($uploadFile->getMimeType(), 'image/')) { Tools::log()->error('file-not-supported'); continue; } $folder = Tools::folder('MyFiles'); Tools::folderCheckOrCreate($folder); $uploadFile->move($folder, $uploadFile->getClientOriginalName()); ``` ### Root Cause - The validation only checks if MIME type contains `"image/"` - This can be bypassed by prepending **GIF89a magic bytes** to a PHP file - The system incorrectly identifies the file as `image/gif` - The file is saved with a `.php` extension in a web-accessible directory ### File Storage Behavior Uploaded files are stored in: ``` /MyFiles/YYYY/MM/X.php ``` Where `X` is an auto-incrementing ID. This allows direct remote execution: ``` http://target/MyFiles/2026/03/2.php?cmd=id ``` --- ## Impact Successful exploitation:

An attacker may upload f…