GHSA-79xx-vf93-p7cx

### Summary The researcher discovered zero-day vulnerability Cross-Site Scripting (XSS) vulnerability in the code which translates the XLSX file into a HTML representation and displays it in the response.

### Details When generating the HTML from an xlsx file containing multiple sheets, a navigation menu is created. This menu includes the sheet names, which are not sanitized. As a result, an attacker can exploit this vulnerability to execute JavaScript code.

```php // Construct HTML $html = '';

// Only if there are more than 1 sheets if (count($sheets) > 1) { // Loop all sheets $sheetId = 0;

$html .= '<ul class="navigation">' . PHP_EOL;

foreach ($sheets as $sheet) { $html .= ' <li class="sheet' . $sheetId . '"><a href="#sheet' . $sheetId . '">' . $sheet->getTitle() . '</a></li>' . PHP_EOL; ++$sheetId; }

$html .= '</ul>' . PHP_EOL; } ```

### PoC 1. Create an XLSX file with multiple sheets : 

2. Generate the HTML content ```php <?php require __DIR__ . '/vendor/autoload.php';

$inputFileName = 'payload.xlsx'; $spreadsheet = \PhpOffice\PhpSpreadsheet\IOFactory::load($inputFileName); $writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet); $writer->writeAllSheets(); echo $writer->generateHTMLAll(); ?> ``` 3. Enjoy 

### Impact

XSS can cause a variety of problems for the end user that range in severity from an annoyance to complete account compromise. Example of impacts :

- Disclosure of the user’s session cookie, allowing an attacker to hijack the user’s session and take over the account (Only if HttpOnly cookie's flag is set to false). - Redirecting the user to some other page or site (like phishing websites) - Modifying the content of the current page (add a fake login page that sends credentials to the attacker). - Automatically download malicious files. - Requests access to the victim geolocation / camera. - ...