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GHSA-44jg-mv3h-wj6g

LowCVSS 1.9 / 10
Published Jan 15, 2026·Last modified Feb 3, 2026
Affected Components(0)

No affected components available

Description

Summary

Short summary of the problem. Make the impact and severity as clear as possible. For example: An unsafe deserialization vulnerability allows any unauthenticated user to execute arbitrary code on the server.

\PhpOffice\PhpSpreadsheet\Writer\Html doesn't sanitize spreadsheet styling information such as font names, allowing an attacker to inject arbitrary JavaScript on the page.

Details

Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer.

See https://github.com/advisories/GHSA-wgmf-q9vr-vww6

PoC

Complete instructions, including specific configuration details, to reproduce the vulnerability.

Example target script:

<?php

require 'vendor/autoload.php';

$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader("Xlsx");
$spreadsheet = $reader->load(__DIR__ . '/book.xlsx');

$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet);
print($writer->generateHTMLAll());

Save this file in the same directory:

book.xlsx

Open index.php in a web browser. An alert should be displayed.

Impact

What kind of vulnerability is it? Who is impacted?

Full takeover of the session of users viewing spreadsheet files as HTML.

Risk Scores
Base Score
1.9

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges.

Threat Intelligence
1.1

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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