I recently found out Travis CI is ending its free-for-opensource offering, and looked at the alternatives. I recently got badly burned by giving an external CI service access to my repositories, so I am now wary of giving any service any access to important accounts. Github Actions, being a part of Github, therefore looked attractive to me. I had no experience with Github Actions going in. I have now spent maybe 4 hours total tinkering with it.
The Kinsing attack has recently been reported by security researchers, and it is well known for targeting misconfigured cloud native environments. It is also known for its comprehensive attack patterns, as well as defense evasion schemes. A misconfigured host or cluster could be exploited to run any container desired by the attacker. That would cause outages on your service or be used to perform lateral movement to other services, compromising your data.