CVE-2026-35453: PhpSpreadsheet has XSS via NumberFormat @ Text Substitution in HTML Writer

April 28, 2026 (updated May 8, 2026)

The HTML Writer in PhpSpreadsheet bypasses htmlspecialchars() output escaping when a cell uses a custom number format containing the @ text placeholder with additional literal text (e.g., @ "items" or "Total: "@). This allows an attacker to inject arbitrary HTML and JavaScript into the generated HTML output by crafting a malicious XLSX file.

References

github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-6wpp-88cp-7q68
github.com/advisories/GHSA-6wpp-88cp-7q68
nvd.nist.gov/vuln/detail/CVE-2026-35453

Code Behaviors & Features

Detect and mitigate CVE-2026-35453 with GitLab Dependency Scanning

Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Dependency Scanning using SBOM also detects vulnerabilities from proprietary advisories that this site does not include. Learn more about Dependency Scanning using SBOM →