Long story short: they messed up the assign-reviewers.yml workflow, allowing external contributors to merge PRs without proper reviews. From this point on, you're fully open to all kinds of bad stuff.
The workflow was configured in a way that allowed untrusted code from a branch controlled by the attacker to be executed in the context of a GitHub action workflow that had access to secrets.
Why does it need to be a distinct product and not Cursor/ChatGPT/Claude code/any of the other existing tools?
(If you're so anti-AI that you're still writing boilerplate like that by hand, I mean, not gonna tell you what you do, but the rest of us stopped doing that crap as soon as it was evident we didn't have to any more.)
The attacker did not need to merge any PRs to exfiltrate the credentials