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

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.