Welcome to the old cage. Some stuff never gets old and some stuff continues to be insecure. Find and exploit a flaw in the GitHub Actions workflow of this repository.
To do so, create a fork of this repository and then create a pull request from the fork against this repository.
To add team members/collaborators, create a new issue in this repository with the content /add @change-me-as-this-user-does-not-exist ....
Please test your exploit first against your own fork, before testing against this instance, because GitHub Actions minutes are limited.
If you want to debug the actions, there is a special debug version. To use this version, enable GitHub Actions in your fork and create a pull request from your fork against your fork repository itself. The action will then run and afterwards you'll have a chance to use tmate to SSH into the machine.