Harness CI now integrates with GitHub Actions, enabling users to utilize over 10,000 pre-built actions from the GitHub marketplace in their continuous integration pipelines, thereby enhancing automation, efficiency, and flexibility. This integration allows GitHub Actions to be used as plugin steps within Harness CI, facilitating tasks such as code cloning, Docker image building, and vulnerability scanning. The process involves specifying attributes like 'name', 'with', and 'env' in the plugin step settings, and running the step in privileged mode due to the use of Docker in Docker (dind). Examples provided include using the Trivy scanning action for vulnerability detection, a GCS upload action for uploading files to Google Cloud Storage, and a Git checkout action for cloning repositories. The integration is supported by nektos/act, which runs a Docker container to execute the GitHub action workflow locally, emphasizing the pluggability and extensibility of Harness CI.