GHSA-wv23-996v-q229 PhpSpreadsheet has a Cross-Site Scripting (XSS) vulnerability in custom properties

• Packagist phpoffice/phpspreadsheet: >= 3.0.0, < 3.7.0 → fixed in 3.7.0 • Packagist phpoffice/phpspreadsheet: < 1.29.7 → fixed in 1.29.7 • Packagist phpoffice/phpspreadsheet: >= 2.0.0, < 2.1.6 → fixed in 2.1.6 • Packagist phpoffice/phpspreadsheet: >= 2.2.0, < 2.3.5 → fixed in 2.3.5 • Packagist phpoffice/phpexcel: <= 1.8.2 (no fix yet)

Cross-Site Scripting (XSS) vulnerability in custom properties 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: 5.4 (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N) CVSS vector v.4.0: 4.8 (AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N) Description: the HTML page is generated without clearing custom properties Impact: executing arbitrary JavaScript code in the browser Vulnerable component: class `PhpOffice\PhpSpreadsheet\Writer\Html`, method `generateMeta` Exploitation conditions: a user viewing a specially generated Excel file Mitigation: additional sanitization of special characters in a string Researcher: Aleksey Solovev (Positive Technologies) Research The researcher discovered zero-day vulnerability Cross-Site Scripting (XSS) vulnerability in custom properties in Phpspreadsheet. The following code is written on the server, which translates the XLSX file into a HTML representation and displays it in the response. *Listing 9. Source code on the server* ``` generateHTMLAll()); ``` An attacker can embed a payload in a file property that will result in the execution of arbitrary JavaScript code. The Excel file is unpacked and a custom property in the file is inserted into the `docProps/custom.xml` file. *Figure 17. Embedding the payload* After making the changes, a new archive with the xlsx extension was created. At the moment of converting the xlsx file into an HTML representation, a property is obtained that participates in the formation of a string without sanitization. *Figure 18. Getting a custom property* When calling the static `generateMeta` method, you can see that the key of the custom property is displayed without sanitization. *Figure 19. Getting a custom property* As a result, when viewing the excel file as the HTML representation, arbitrary JavaScript code will be executed. *Figure 20. Executing arbitrary JavaScript code* Credit This vulnerability was discovered by Aleksey Solovev (Positive Technologies)