attachments.php

<?php

function add_attachments($data = null, $model = null) {
    
    if (!empty($model) && $model == "History") {
        if (!empty($_FILES)) {
            foreach ($_FILES as $fkey => $fval) {
                $data['newattachments'][] = array(
                    'title'             =>  "title for attachment",
                    'filename'          =>  "/absolute/path/to/the/attachment.ext",
                );
            }
        }
    }
    
    return $data;
}

add_filter('newsletters_db_data_before_validate', 'add_attachments', 10, 2);

?>