CVE-2020-15228: Improper Input Validation

In the @actions/core npm module, addPath and exportVariable functions communicate with the Actions Runner over stdout by generating a string in a specific format. Workflows that log untrusted data to stdout may invoke these commands, resulting in the path or environment variables being modified without the intention of the workflow or action author. The runner will release an update that disables the set-env and add-path workflow commands in the near future.