Cross Site Scripting Vulnerability on "Theme Manager" feature in PHP-Fusion 9.03.60 (New Version)

[Songohan22]

Describe the bug
An authenticated malicious user can take advantage of a Reflected XSS vulnerability in the "Thêm Manager" feature. This was can be bypassed by using HTML event handlers, such as "ontoggle".

To Reproduce
Steps to reproduce the behavior:

1. Log into the panel.
2. Go to "/administration/theme.php"
3. Click "Manage Theme"
4. Insert payload '><details/open/ontoggle=confirm(/XSS/)>
5. Click "Save Changes"
6. View the preview to trigger XSS.
7. View the preview to get in request and such Reflected XSS

Expected behavior
The removal of script tags is not sufficient to prevent an XSS attack. You must HTML Entity encode any output that is reflected back to the page.

Screenshots

Desktop (please complete the following information):

• OS: Windows
• Browser: Firefox
• Version: 76.0.1