External risk intelligence

Monkeytype Workflow Vulnerability Allows Arbitrary Code Execution.

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-118762

The vulnerability exists within a CI/CD build-time workflow configuration (.github/workflows) rather than the application itself. It is triggered during the pull request process by developers or contributors and is not accessible to users or public internet traffic. As a build-time and developer-focused component, it lacks typical public-facing network exposure.

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory details a vulnerability in a software development workflow, not the main application. The issue could allow unauthorized code execution and data exfiltration within the development environment if a malicious pull request is accepted and labeled for formatting checks. The primary concern is confirming if this specific development workflow is in use and exposed to external contributors.

Workflow flaw allows code execution.
Confirms relevance and exposure of development process.
Understand development workflow risks.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by submitting a pull request to the project's code repository. If this pull request is approved and given a specific label, it triggers a workflow that can execute arbitrary code. This allows the attacker to potentially read or steal sensitive tokens and then use them to modify repository content, issues, or other pull requests.

Entry condition: Malicious pull request submitted.
Trigger point: Workflow runs on pull request with label.
Resulting risk: Code execution and token exfiltration.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an external contributor to execute arbitrary code within the repository's CI workflow. This is possible when a pull request targeting the repository is created and the `format` label is applied, under specific workflow conditions that involve checking out a fork and installing dependencies from it. The core issue lies in how the GitHub token persists, enabling untrusted code execution.

Repository code and data.
Malicious code execution during PR review.
Unauthorized modification of repository content.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability impacts the Monkeytype CI workflow, not the application or user data, and is likely the responsibility of the Platform or Security Engineering team managing the CI/CD pipeline. The first practical step is to confirm the exact scope of the workflow's reach within your repository and assess the risk associated with the `GITHUB_TOKEN`'s permissions.

Platform/Security Engineering owns the fix.
Verify workflow reach and token permissions.
Update CI workflow to mitigate risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Monkeytype?

Monkeytype is an open-source, minimalistic typing test application. While many people use it for practicing their typing speed and accuracy through a browser, this vulnerability does not impact the application or user data. Instead, the issue is limited to the project's internal CI/CD automation files, specifically those handling automated formatting during the software development process.

What does CWE-829 mean for CVE-2026-118762?

CWE-829 refers to the inclusion of functionality from an untrusted control sphere. In the context of this CVE, it means the development workflow automatically downloads and runs code from external contributors—such as dependencies found in a forked pull request—before the environment is properly secured. This allows unauthorized code to execute using the repository's own security credentials.

How is this vulnerability triggered?

An attacker triggers this by submitting a malicious pull request and having a maintainer apply a specific 'format' label. It is not triggered by normal usage of the Monkeytype typing test, nor by public internet traffic hitting the application. The workflow only runs when this specific collaborative development step occurs, meaning the environment must be configured to process these external contributions.

Why is the risk level low according to Halo Surface Signal?

Halo Surface Signal indicates this is unlikely to affect typical users because the vulnerability resides entirely within build-time configuration files. It is not an internet-facing software flaw. Since the risk is confined to the repository's internal development pipeline, it does not pose a direct threat to the application's public-facing interfaces.

Do I need to update my Monkeytype installation?

No. Because the issue is contained within the CI/CD workflow and not the typing application itself, updating the app will not resolve the underlying risk. If you are a developer or maintainer working on the repository, you should upgrade to version 26.43.0 or later to patch the workflow configuration and protect your development environment tokens.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.