Monkeytype’s CI workflow ran on pull_request_target with repository write permissions, checking out forked code and invoking a fork‑controlled binary. The checkout action persisted the GITHUB_TOKEN in Git configuration, giving a contributor who received the format label the ability to execute arbitrary code that could read or exfiltrate the token and use it to push unrestricted content or alter pull requests and issues. The vulnerability allows an attacker to read repository secrets and modify or replace repository files, but does not affect the runtime application or end user data. The weakness is a credential exploitation flaw.

Monkeys Monkeytype repository (monkeytypegame:monkeytype) versions prior to 26.43.0 are affected. No specific patch version list is provided beyond the note that v26.43.0 contains the fix.

The CVSS score of 9.3 marks it as critical. EPSS data is unavailable, but the KEV catalog does not list this issue. The likely attack vector is an external contributor submitting a pull request that triggers the vulnerable workflow; the attack requires no privileged network access beyond the PR submission. Given the high severity and the fact that the workflow grants full repository write access, the risk of exploitation is high if the CI remains running on forks.