Idk, feels like free speech to me. If the prompt injection is in code with a typical "no warranty" license, then I don't see how there could be any liability. It's indistinguishable from joking and sarcasm like people talking about "rm -rf /" for the memes.

There's maybe some limited scenarios where it could end up in a lawsuit, like if a company selling services ended up prompt injecting their customers, since there's an actual service contract involved.