Word documents generated by PHPWord 0.14/0.16 are incompatible with "finfo" and "file" bytestream mimetype guessers

[vitanivanov]

The mimetype of Word2007 documents generated by PHPWord 0.14/0.16 cannot be determined correctly neither by Ubuntu 16.04 "file" command nor by PHP 7.2 finfo's bytestream mimetype guesser.

Ubuntu's file command and PHP 7.2's finfo command both read the files as binary and determine their mimetype based on logic, which parses the file's bytestream hexadecimal values.

When determining the mimetype of Word2007 documents generated by PHPWord 0.14/0.16, both executables fail to do so, hence returning "application/octet-stream".

In our application we rely on determining the mimetype, instead of trusting the meta info "Content-Type". Due to security reasons we don't allow uploading "application/octet-stream" which makes it impossible for us to upload files, generated by ourselves using PHPWord.

Steps to Reproduce

1. Execute the following code, taken from PHPWord's documentation

<?php
require __DIR__ . '/vendor/autoload.php';

            $phpWord = new \PhpOffice\PhpWord\PhpWord();
            $section = $phpWord->addSection();
            $section->addText( '"Learn from yesterday, live for today, hope for tomorrow. '
                . 'The important thing is not to stop questioning." (Albert Einstein)');
            $objWriter = \PhpOffice\PhpWord\IOFactory::createWriter($phpWord, 'Word2007');
            $objWriter->save('helloWorld.docx');

2. Execute "file --mime-type -b {PATH_TO_FILE}"

Expected Behavior

"application/vnd.openxmlformats-officedocument.wordprocessingml.document" is returned

Current Behavior

"application/octet-stream" is returned

Context

• PHP Version: 7.2
• PHPWord Version: 0.14, 0.16