https://media.ccc.de/v/39c3-skynet-starter-kit-from-embodied...
> [...] we also exploit the embodied AI agent in the robots, performing prompt injection and achieve root-level remote code execution.
I guess you could argue that github wasn't vulnerable in this case, but rather the author of the action, but it seems like it at least rhymes with what you're looking for.
These folks have found a bunch: https://www.promptarmor.com/resources
But I guess you mean one that has been exploited in the wild?