CVE-2026-118762: Monkeytype: fork PR can execute code with elevated GITHUB_TOKEN
Monkeytype is a minimalistic and customizable typing test. Prior to 26.43.0, the .github/workflows/fix-formatting.yml workflow runs on pullrequesttarget with repository write permissions, checks out a fork pull request, installs dependencies from the fork's package.json, and invokes the fork-controlled oxfmt binary. Because actions/checkout persists the elevated GITHUBTOKEN in Git configuration until after untrusted code executes, an external contributor whose pull request receives the format label can run arbitrary code, read or exfiltrate the token, and push repository content or modify pull requests and issues. The issue affects the repository CI workflow, not the Monkeytype application or user data. This issue is fixed in version 26.43.0.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Monkeytypeto a version that resolves this vulnerability.Fixed in 26.43.0
Event History
Frequently Asked Questions
Who can exploit this issue?
An external contributor can exploit it by submitting a pull request from a fork and having that pull request receive the format label. No prior repository permissions are required.
What access could an attacker gain through the workflow?
The attacker can execute arbitrary code in the CI workflow, read or exfiltrate the elevated GITHUB_TOKEN, and use it to push repository content or modify pull requests and issues.
Are Monkeytype application deployments or user data affected?
No. The issue affects the repository CI workflow rather than the Monkeytype application or its user data.
How can maintainers determine whether they are vulnerable?
Repositories using a version prior to 26.43.0 are affected if their fix-formatting workflow runs on pull_request_target with repository write permissions, checks out fork pull requests, and installs or invokes fork-controlled dependencies or binaries.
What should maintainers do if they cannot immediately upgrade?
The provided information does not specify a workaround. Until the fix is applied, avoid allowing the affected formatting workflow to run against fork pull requests that can control package.json or the invoked oxfmt binary.