SB2026042739 - Multiple vulnerabilities in PhpSpreadsheet

Description

This security bulletin contains information about 2 secuirty vulnerabilities.

1) Cross-site scripting (CVE-ID: CVE-2026-35453)

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data within NumberFormat @ Text Substitution in HTML Writer. A remote attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

2) Stored cross-site scripting (CVE-ID: CVE-2026-40296)

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data within number format code with @ text placeholder. A remote user can inject and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

Remediation

Install update from vendor's website.

References

• https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-6wpp-88cp-7q68
• https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-hrmw-qprp-wgmc