GHSA-r8w8-74ww-j4wh

### Summary `\PhpOffice\PhpSpreadsheet\Writer\Html` does not sanitize "javascript:" URLs from hyperlink `href` attributes, resulting in a Cross-Site Scripting vulnerability.

### PoC

Example target script:

``` <?php

require 'vendor/autoload.php';

$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader("Xlsx"); $spreadsheet = $reader->load(__DIR__ . '/book.xlsx');

$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet); print($writer->generateHTMLAll()); ```

Save this file in the same directory: [book.xlsx](https://github.com/PHPOffice/PhpSpreadsheet/files/15099763/book.xlsx)

Open index.php in a web browser and click on both links. The first demonstrates the vulnerability in a regular hyperlink and the second in a HYPERLINK() formula.