Suggestion about research plan I would like to apply for PhD studies in Computer Science in a university in Europe, but I have seen that among the requirements is a brief research plan.

Let's suppose that the field in which they are offering the PhD is in topic X focused in Y. For what I know the research plan is the outcome of an agreement between the potential supervisor and the applying PhD student; so what to put there if I only know X and Y, but still have not contacted any of the supervisors (the application does not say explicitly to do so)?

Comment: I know about topic X and a little bit about the specialized topic Y, but I am afraid that if I propose to do some research in Y, maybe, it would appear as a numb or dry topic to them and I end up losing this opportunity.

Any help?
As much as anything, the purpose of the research proposal (in the UK at least) is to show potential supervisers that you have the ability to construct and justify academic research, can write clearly and put forward coherent arguments. It is unlikely that you would be held to the specifics of your proposal. Once you have been accepted somewhere, it is generally accepted that the details of your research will (at least) be refined, if not completely changed! Just think of it as a way of demonstrating your abilities.