I caught someone using a pull request against one of my GitHub repositories to trigger crypto-currency mining via a GitHub action. I took a snapshot of it with archive-web-page here after reporting it to GitHub:
https://inkdroid.org/web-archives/github-bitcoin-mining/
It seems like this is a thing now: https://www.bleepingcomputer.com/news/security/github-actions-being-actively-abused-to-mine-cryptocurrency-on-github-servers/ The only way to turn it off is to only run actions that are defined by the repository?
FWIW I'm glad I took a snapshot of the pull request pages with https://archiveweb.page because GitHub have deleted the PR, so it's like it never existed.