phpoffice/phpspreadsheet is a pure PHP library for reading and writing spreadsheet files. Affected versions have been found to have a Bypass of the Cross-site Scripting (XSS) sanitizer using the javascript protocol and special characters. This issue has been addressed in versions 3.9.0, 2.3.7, 2.1.8, and 1.29.9. Users are advised to upgrade. There are no known workarounds for this vulnerability.