CVE-2025-66469
NiceGUI Reflected XSS in ui.add_css, ui.add_scss, and ui.add_sass via Style Injection
Vexday Risk Score
13Low
SSVC decision (CISA)
Track
No exploitation signal → monitor
CVSS 6.1EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —
Lifecycle
08 Dec 2025Published on NVD
Recommendation: Monitor — no exploitation signal at the moment.
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Affected products
zauberzeug · niceguiWant to know if your infrastructure is exposed to this?
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