Between the apparently-probabilistic nature of LLMs deciding which instructions ought to be followed, and the possibility of an LLM simply hallucinating a convincing-and-embarrassing prompt anyway, there will probably always be “attacks” that leak prompts.

People seem to approach this with a security mindset of finding and patching exploits, but I don’t really think it is a security issue. These prompts are for UX, after all. Maybe the right perspective is that prompt leaks are sort of like “view source” on a webpage; make sure proprietary business logic isn’t in client-side JavaScript and avoid embarrassing dark patterns like

    if (mobileWebSite) {
        serveAdForNativeApp(); 
        await sleep(5000); 
    }