Numerous significant questions are left unanswered, including what, if anything, Mr. Assange knew about the identity of Guccifer 2.0, a mysterious hacker who American intelligence and law enforcement officials have identified as a front for Russian military intelligence operatives.

Court documents have revealed that it was Russian intelligence — using the Guccifer persona — that provided Mr. Assange thousands of emails hacked from the Democratic National Committee and the personal account of John D. Podesta, the chairman of the Clinton campaign.

Another question is whether Mr. Assange was a conduit between the Russian hackers and the Trump campaign. Mr. Assange exchanged emails with Donald Trump Jr., Mr. Trump’s eldest son, during the campaign, and a Trump campaign official sent Roger J. Stone Jr., a longtime adviser to the president, to get information about the hacked Democratic emails, according to a January indictment by Robert S. Mueller III, the special counsel.

Mr. Mueller concluded his investigation without an indictment that directly connected WikiLeaks, the Russians and the Trump campaign, suggesting that prosecutors did not find sufficient evidence that Mr. Assange knowingly engaged in a conspiracy with Russia to help the Trump campaign.

But the report drafted by Mr. Mueller’s team, and expected to be released next week, could have additional details about the ties between the Trump campaign and Mr. Assange. Those details could be redacted by the Justice Department, however, if officials believe the material includes classified intelligence, said Carrie Cordero, a former official with the Justice Department’s National Security Division and the Office of the Director of National Intelligence.