CVE-2025-66469

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

6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

0.3% chance of exploitation in the next 30 days; higher than 19% of CVEs (scores of 2026-10-25)

CWE

CWE-79

Published

2025-12-09

Modified

2026-10-19

Record from

the NVD, synced 2026-10-19

Affected

• zauberzeug:nicegui

Packages (OSV)

References

• https://github.com/zauberzeug/nicegui/commit/a8fd25b7d5e23afb1952d0f60a1940e18b5f1ca8
• https://github.com/zauberzeug/nicegui/security/advisories/GHSA-72qc-wxch-74mg
• https://github.com/zauberzeug/nicegui/security/advisories/GHSA-72qc-wxch-74mg

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