CVE-2026-40296 PhpSpreadsheet vulnerable to XSS in HTML writer via custom number format codes

PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. The HTML writer skips htmlspecialchars escaping when a cell's formatted value differs from the original value. When a cell has a custom number format containing the text placeholder @ along with any additional literal...

PhpSpreadsheet cross-site scripting vulnerabilities

PhpSpreadsheet is a PHP library developed by PHPOffice, designed for reading and writing spreadsheet files. PhpSpreadsheet has a cross-site scripting vulnerability. This vulnerability arises when the HTML Writer skips htmlspecialchars output escaping when using custom number formats that contain ...