PhpSpreadsheet allows bypassing of XSS sanitizer using the javascript protocol and special characters
Date: 2025-02
Affected: composer/phpoffice/phpexcel, composer/phpoffice/phpspreadsheet, composer/phpoffice/phpspreadsheet
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2025-23210
CWE: CWE-79
CVSS: 5.4 (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N)

**Product:** PhpSpreadsheet **Version:** 3.8.0 **CWE-ID:** CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') **CVSS vector v.3.1:** 5.4 (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N) **CVSS vector v.4.0:** 4.8 (AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N) **Description:** an attacker can use special characters, so that the library processes the javascript protocol with special characters and generates an HTML link **Impact:** executing arbitrary JavaScript code in the browser **Vulnerable component:** class `PhpOffice\PhpSpreadsheet\Writer\Html`, method `generateRow` **Exploitation conditions:** a user viewing a specially generated xml file **Mitigation:** additional sanitization of special characters in a string **Researcher: Igor Sak-Sakovskiy (Positive Technologies)** # Research The researcher discovered zero-day vulnerability Bypass XSS sanitizer using the javascript protocol and special characters in Phpspreadsheet. The following code is written on the server, which translates the XML file into an HTML representation and displays it in the response. *Listing 4. Source code on the server* ``` <?php require __DIR__ . '/vendor/autoload.php'; $inputFileType = 'Xml'; $reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType); $inputFileName = './doc/file.xml'; $spreadsheet = $reader->load($inputFileName); $writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet); print($writer->generateHTMLAll(


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