# CVE-2025-66563: Monkeytype vulnerable to stored XSS in approve quotes page

> Attackers can execute malicious JavaScript on other users' browsers by submitting quotes containing HTML tags in the Monkeytype typing test application.

- **Severity:** High 7.1 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 4 Dec 2025
- **Updated:** 5 Dec 2025
- **Also known as:** GHSA-mfjh-9552-8g27

## What is CVE-2025-66563?

CVE-2025-66563 is a high-severity cross-site scripting vulnerability in monkeytypegame monkeytype, published on 4 Dec 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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).

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2025-66563?

It affects 1 product.


Products: Monkeytype Monkeytype.

## How do I fix CVE-2025-66563?

No fix has been published for CVE-2025-66563 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-66563 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66563 exists.

## Other vulnerabilities in monkeytypegame monkeytype

- [CVE-2024-41127](https://insights.sbomify.com/CVE-2024-41127/): Code injection in monkeytype (high 8.4)
- [CVE-2025-59838](https://insights.sbomify.com/CVE-2025-59838/): Monkeytype Vulnerable to Self-XSS on loading saved custom text (low 2.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66563 and fix it if it is affected.

What it is: CVE-2025-66563 is a high-severity cross-site scripting vulnerability in monkeytypegame monkeytype, published on 4 Dec 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66563 exists.

Affected product: monkeytypegame monkeytype. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-66563/ (Markdown: https://insights.sbomify.com/CVE-2025-66563/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66563
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66563
- OSV: https://osv.dev/vulnerability/CVE-2025-66563

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-66563/
Summaries are generated and may contain mistakes; the official description above is the record.