GHSA-wgmf-q9vr-vww6

PhpSpreadsheet HTML writer is vulnerable to Cross-Site Scripting via style information

### Summary `\PhpOffice\PhpSpreadsheet\Writer\Html` doesn't sanitize spreadsheet styling information such as font names, allowing an attacker to inject arbitrary JavaScript on the page. ### 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/15212797/book.xlsx) Open index.php in a web browser. An alert should be displayed. ### Impact Full takeover of the session of users viewing spreadsheet files as HTML.