Well, Senator Paul has tweeted his question (name redacted in accordance with third party request):
Can't the Chief Justice block any question he wants?
This is a different question and it's better addressed in a different answer here. To quote from that answer:
Procedure and Guidelines for Impeachment Trials in the United States Senate, pp. 3, 5.
And the Presiding Officer on the trial may rule on all questions of evidence including, but not limited to, questions of relevancy, materiality, and redundancy of evidence and incidental questions, which ruling shall stand as the judgment of the Senate, unless some Member of the Senate shall ask that a formal vote be taken thereon, in which case it shall be submitted to the Senate for decision without debate; or he may at his option, in the first instance, submit any such question to a vote of the Members of the Senate. Upon all such questions the vote shall be taken in accordance with the Standing Rules of the Senate.
So the presiding officer, in this case Chief Justice Roberts, may rule to block a question. A senator could move to challenge that and ask for a formal vote. I don't know, however, how that would work exactly as reasonably you'd have to know the question to vote on it.