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Vulnerability record · CVE-2025-66469 · published 9 December 2025

CVE-2025-66469: Zauberzeug nicegui cross-site scripting vulnerability

Zauberzeug · Nicegui

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.

6.1 CVSS 3.1 Medium EPSS 0.27% · top 81.9% CWE-79 · Cross-site scripting
6.1CVSS 3.1 base score
0.27%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/zauberzeug/nicegui/commit/a8fd25b7d5e23afb1952d0f60a1940e18b5f1ca8 Patch
https://github.com/zauberzeug/nicegui/security/advisories/GHSA-72qc-wxch-74mg ExploitVendor Advisory
https://github.com/zauberzeug/nicegui/security/advisories/GHSA-72qc-wxch-74mg ExploitVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2025-66469), CISA KEV, FIRST EPSS (scores of 2026-10-03). This page is refreshed as NVD updates the record.