Magento LTS vulnerable to stored XSS in admin file form

Summary

OpenMage is affected by a stored Cross-Site Scripting (XSS) vulnerability that could be abused by a low-privileged attacker to inject malicious scripts into vulnerable form fields.

Details

Mage_Adminhtml_Block_System_Config_Form_Field_File does not escape filename value in certain situations.
Same as: https://nvd.nist.gov/vuln/detail/CVE-2024-20717

PoC

1. Create empty file with this filename: <img src>.crt
2. Go to System > Configuration > Sales | Payment Methonds.
3. Click Configure on PayPal Express Checkout.
4. Choose API Certificate from dropdown API Authentication Methods.
5. Choose the XSS-file and click Save Config.
6. Profit, alerts “1” -> XSS.
7. Reload, alerts “1” -> Stored XSS.

Impact

Affects admins that have access to any fileupload field in admin in core or custom implementations.
Malicious JavaScript may be executed in a victim’s browser when they browse to the page containing the vulnerable field.