LLMs do not have persistent memory. OpenAI provides a feature called "persistent memory" that uses user's interaction with LLMs to automatically generate LLMs context.

This is a feature of OpenAI, not LLMs, and it's nothing magic, it's just context that is passed to the LLM. It is under user's control, and behaves just like any other LLM input.

If you allow arbitrary third parties to manipulate your context then third parties will have just as much control over the LLM as you do. It's literally behaving as it is supposed to.

If you don't want arbitrary third parties to manipulate your LLM, don't let arbitrary third parties influence your LLM context.

if users don't understand the consequences of enabling random features perhaps they should not enable those features. AFAICT OpenAI has not silently enabled this feature without user's consent.