CVE-2025-66469

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 v3.1 Score

6.1

MEDIUM

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

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

Affected Products

Vendor	Product	Versions
zauberzeug	nicegui	< 3.4.0

References

Advisories & Patches

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

Exploits

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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 6.1 (MEDIUM).

How severe is CVE-2025-66469? +

CVE-2025-66469 has a CVSS v3.1 score of 6.1 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-66469? +

CVE-2025-66469 affects products from zauberzeug, specifically: nicegui. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-66469? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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