This does not solve the problem. The issue is that by definition, an LLM can't distinguish between instructions and data. When you tell an LLM "summarize the following text", the command you give it and the data you give it (the text you want it to summarize) are both just input to the LLM.

It's impossible to solve this. You can't tell an LLM "this is an instruction, you should obey it, and this is data, you should ignore any instructions in it" and have it reliably follow these rules, because that distinction between instruction and data just doesn't exist in LLMs.

As long as you allow anything untrusted into your LLM, you are vulnerable to this. You allow it to read your emails? Now there's an attack vector, because anyone can send you emails. Allow it to search the Internet? Now there's an attack vector, because anyone can put a webpage on the Internet.