CVE-2025-22131: Cross-Site Scripting Vulnerability in PhpSpreadsheet

Introduction

PhpSpreadsheet is a widely-used PHP library for reading and writing spreadsheet files. It allows developers to easily handle Excel and other spreadsheet formats (XLSX, CSV, etc.) within PHP applications. However, a recent vulnerability identified as CVE-2025-22131 has been discovered in PhpSpreadsheet that could allow an attacker to inject malicious scripts into the application, leading to Cross-Site Scripting (XSS) attacks.

In this blog post, we'll discuss the nature of the vulnerability, its potential impact, and how to mitigate it.

The Vulnerability

CVE-2025-22131 is a Cross-Site Scripting (XSS) vulnerability in PhpSpreadsheet that occurs when the library is used to convert an XLSX file into an HTML representation. The flaw specifically arises during the process of displaying the translated content in the response. Attackers can exploit this issue by crafting an XLSX file containing malicious JavaScript payloads, which, when rendered as HTML, can execute on the client-side.

When the affected PhpSpreadsheet version renders the spreadsheet content into HTML, it fails to properly sanitize certain input, allowing malicious scripts embedded in the XLSX file to be executed in the user's browser. This could lead to a variety of attacks, including:

  • Session hijacking through stealing cookies.
  • Phishing attempts via fake login forms.
  • Defacement of the web application.
  • Data theft through unauthorized access to sensitive user information.

How the Vulnerability Works

1. XLSX File with Malicious Code: The attacker creates an XLSX file containing payloads in cells or headers. These payloads could be JavaScript embedded in the file in various ways, such as through cell values, hyperlinks, or other elements within the spreadsheet.

2. Rendering in HTML: When the vulnerable version of PhpSpreadsheet processes and converts the XLSX file to HTML for presentation on a web page, it fails to escape or sanitize the embedded scripts.

3. Execution of the Script: As the HTML representation is sent back to the user’s browser, the malicious scripts are executed within the context of the application. This could compromise the security of the application or the user's session.

Affected Versions

This vulnerability affects PhpSpreadsheet versions before the fix was introduced in the commit: PhpSpreadsheet GitHub Commit

Mitigation

To mitigate this issue, it is highly recommended that all users of PhpSpreadsheet update to the latest version where the vulnerability has been patched. If you are unable to upgrade immediately, consider the following workarounds:

  • Sanitize Input: Ensure that any content being processed through PhpSpreadsheet is sanitized before rendering it in an HTML response. This can be done by using proper encoding and escaping mechanisms.
  • Use Content Security Policies (CSP): Implement strict CSP headers to limit the types of scripts that can be executed in your application, reducing the risk of XSS attacks.
  • Upgrade PhpSpreadsheet: The simplest and most effective mitigation is to upgrade PhpSpreadsheet to the patched version, which addresses this vulnerability.

References

Conclusion

Cross-Site Scripting vulnerabilities like CVE-2025-22131 can be incredibly dangerous, especially when they allow an attacker to inject malicious code that affects a large number of users. PhpSpreadsheet's vulnerability is an important reminder of the need for proper input validation and sanitization in all PHP applications, particularly those dealing with user-generated content or file uploads. Always keep your libraries up-to-date to ensure your applications remain secure.