GHSA-c5qx-p38x-qf5w

Summary

Log output includes authentication token that provides full account access

Details

The post job action prints the contents of config/config.vdf which holds the saved authentication token and can be used to sign in on another machine. This means any public use of this action leaves authentication tokes for the associated steam accounts publicly available. Additionally, userdata/$user_id$/config/localconfig.vdf contains potentially sensitive information which should not be included in public logs.

PoC

Use the following workflow step

steps:
      - name: Setup SteamCMD
        uses: buildalon/setup-steamcmd@v1.0.4

      - name: Sign into steam
        shell: bash
        run: |
          steamcmd +login ${{ secrets.WORKSHOP_USERNAME }} ${{ secrets.WORKSHOP_PASSWORD }} +quit

Impact

Anyone who has used this workflow action with a steam account is affected and has had valid authentication tokens leaked in the job logs. This is particularly bad for public repositories, as anyone with a GitHub account can access the logs and view the token.