CVE-2025-66563

Name: CVE-2025-66563
Creator: NVD / NIST
Published: 2025-12-04T23:15:47.27+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.1/10EPSS 0.20%

Last modified Jun 17, 2026

CVE-2025-66563 is a high-severity vulnerability rated 7.1/10 on the CVSS scale. Monkeytype is a minimalistic and customizable typing test. In 25.49.0 and earlier, there is improper handling of user input which allows an attacker to execute malicious javascript on anyone viewing a malicious quote submission. EPSS estimates a 0.20% chance of exploitation in the next 30 days.

Description

Monkeytype is a minimalistic and customizable typing test. In 25.49.0 and earlier, there is improper handling of user input which allows an attacker to execute malicious javascript on anyone viewing a malicious quote submission. quote.text and quote.source are user input, and they're inserted straight into the DOM. If they contain HTML tags, they will be rendered (after some escaping using quotes and textarea tags).

Metrics

CVSS 3.1

6.1/10

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

CVSS 4.0

7.1/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.20%

9.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Monkeytype	Monkeytype	<= 25.49.0

References

https://github.com/monkeytypegame/monkeytype/commit/d6d062a77132ba7d6ba3b482d46ae329d3b8d695Patch
https://github.com/monkeytypegame/monkeytype/security/advisories/GHSA-mfjh-9552-8g27Exploit, Vendor Advisory
https://github.com/monkeytypegame/monkeytype/security/advisories/GHSA-mfjh-9552-8g27Exploit, Vendor Advisory

Timeline

Published: Dec 4, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-66563?

How severe is CVE-2025-66563?

CVE-2025-66563 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 0.20% probability of exploitation in the next 30 days.

How do I fix CVE-2025-66563?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-66563?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST