Product: Phpspreadsheet
Version: version 3.6.0
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: the HTML page is generated without clearing custom properties
Impact: executing arbitrary JavaScript code in the browser
Vulnerable component: class PhpOffice\PhpSpreadsheet\Writer\Html
, method generateMeta
Exploitation conditions: a user viewing a specially generated Excel file
Mitigation: additional sanitization of special characters in a string
Researcher: Aleksey Solovev (Positive Technologies)
The researcher discovered zero-day vulnerability Cross-Site Scripting (XSS) vulnerability in custom properties in Phpspreadsheet. The following code is written on the server, which translates the XLSX file into a HTML representation and displays it in the response.
Listing 9. Source code on the server
<?php
require __DIR__ . '/vendor/autoload.php';
$inputFileName = './doc/Book1.xlsx';
$spreadsheet = \PhpOffice\PhpSpreadsheet\IOFactory::load($inputFileName);
$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet);
print($writer->generateHTMLAll());
An attacker can embed a payload in a file property that will result in the execution of arbitrary JavaScript code.
The Excel file is unpacked and a custom property in the file is inserted into the docProps/custom.xml
file.
Figure 17. Embedding the payload
After making the changes, a new archive with the xlsx extension was created. At the moment of converting the xlsx file into an HTML representation, a property is obtained that participates in the formation of a string without sanitization.
Figure 18. Getting a custom property
When calling the static generateMeta
method, you can see that the key of the custom property is displayed without sanitization.
Figure 19. Getting a custom property
As a result, when viewing the excel file as the HTML representation, arbitrary JavaScript code will be executed.
<img width="356" alt="fig20" src="https://github.com/user-attachments/assets/a6ed21e3-685c-415c-b2dc-453bc0652bef" />
Figure 20. Executing arbitrary JavaScript code
This vulnerability was discovered by Aleksey Solovev (Positive Technologies)
{ "nvd_published_at": "2025-01-03T18:15:15Z", "cwe_ids": [ "CWE-79" ], "severity": "MODERATE", "github_reviewed": true, "github_reviewed_at": "2025-01-03T17:25:45Z" }