The vulnerability stems from improper validation of user-controlled configuration values that govern file upload restrictions. Key functions identified are those responsible for 1) retrieving allowed extensions from config.php (ImageUploader::getAllowedExtensions), and 2) enforcing these restrictions during upload (Uploader::_setUploadFile). These functions become vulnerable when configuration values are manipulated to empty, as they lack fallback mechanisms to enforce minimum security constraints. The assessment aligns with Magento's architecture where configuration-driven upload filters are common, and matches the CWE-434 pattern of unrestricted uploads via missing validation.