GHSA-44jg-mv3h-wj6g solspace/craft-freeform Vulnerable to XSS in `PhpSpreadsheet` HTML Writer Due to Unsanitized Styling Data

• Packagist solspace/craft-freeform: < 4.1.23 → fixed in 4.1.23

Summary _Short summary of the problem. Make the impact and severity as clear as possible. For example: An unsafe deserialization vulnerability allows any unauthenticated user to execute arbitrary code on the server._ \PhpOffice\PhpSpreadsheet\Writer\Html doesn't sanitize spreadsheet styling information such as font names, allowing an attacker to inject arbitrary JavaScript on the page. Details _Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer._ See https://github.com/advisories/GHSA-wgmf-q9vr-vww6 PoC _Complete instructions, including specific configuration details, to reproduce the vulnerability._ Example target script: ``` load(__DIR__ . '/book.xlsx'); $writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet); print($writer->generateHTMLAll()); ``` Save this file in the same directory: book.xlsx Open index.php in a web browser. An alert should be displayed. Impact _What kind of vulnerability is it? Who is impacted?_ Full takeover of the session of users viewing spreadsheet files as HTML.