CVE-2025-66469
Medium
Description
NiceGUI is a Python-based UI framework. Versions 3.3.1 and below are vulnerable to Reflected XSS through its ui.add_css, ui.add_scss, and ui.add_sass functions. The functions lack proper sanitization or encoding for the JavaScript context they generate. An attacker can break out of the intended <style> or <script> tags by injecting closing tags (e.g., </style> or </script>), allowing for the execution of arbitrary JavaScript. This issue is fixed in version 3.4.0.
SeverityMedium
CVSS6.1
Exploit probability—
ProductZauberzeug Nicegui
PublishedDec 9, 2025
First seenDec 9, 2025
Weakness typeCWE-79Cross-site scripting (XSS)
How to fix
Update
- zauberzeug nicegui3.4.0 or later
- nicegui3.4.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| zauberzeug nicegui | v < 3.4.0 | 3.4.0 |
| niceguiPyPI | v < 3.4.0 | 3.4.0 |
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