A court document filed by mistake has revealed that the Justice Department has filed undisclosed criminal charges against WikiLeaks founder Julian Assange.

In a slip unearthed by a former U.S. intelligence official and posted on Twitter, Assange’s name appears twice in an August court filing by a federal prosecutor in Virginia — an argument to keep sealed an unrelated case involving an accused child sex criminal.

The prosecutor wrote that the charges and arrest warrant “would need to remain sealed until Assange is arrested in connection with the charges in the criminal complaint and can therefore no longer evade or avoid arrest and extradition in this matter.”

At another point in the document, the prosecutor wrote that “due to the sophistication of the defendant and the publicity surrounding the case, no other procedure is likely to keep confidential the fact that Assange has been charged.”

It's not clear what allegations could be connected to the filing, which was a motion to seal a complaint and supporting documents in the unrelated case.

However, special counsel Robert Mueller earlier this year cited WikiLeaks participation in Russia’s efforts to interfere in the 2016 election. U.S. intelligence agencies have said that WikiLeaks disclosed thousands of emails stolen in a covert Russian intelligence operation to help Donald Trump and hurt Hillary Clinton.

Seamus Hughes, deputy director of the Program on Extremism at George Washington University, noticed that Assange's name was in the filing, and he tweeted about it. Hughes is also a former official at the National Counterterrorism Center.

On Thursday night, WikiLeaks' Twitter account further publicized the filing.

SCOOP: US Department of Justice "accidentally" reveals existence of sealed charges (or a draft for them) against WikiLeaks' publisher Julian Assange in apparent cut-and-paste error in an unrelated case also at the Eastern District of Virginia. https://t.co/wrjlAbXk5Z pic.twitter.com/4UlB0c1SAX — WikiLeaks (@wikileaks) November 16, 2018

Joshua Stueve, a spokesman for the U.S. Attorney in the Eastern District of Virginia, said in a statement that that court filing "was made in error. That was not the intended name for this filing."

The filing was first reported by The Washington Post.

WikiLeaks and Assange loom large in the investigation of Russian influence on the election.

The website released unflattering Hillary Clinton campaign emails beginning Oct. 7, 2016, just weeks before the presidential election.

Mueller, who's directing a federal inquiry into election meddling, in July charged 12 Russian intelligence officers with conspiring to hack Democratic National Committee computers in an effort to disrupt the 2016 election. The indictment referred to WikiLeaks as “Organization 1,” and described its role in receiving and disseminating the emails, without addressing whether Assange knew the material came from the Russians.

Barry Pollack, a U.S. lawyer representing Assange, criticized the move to charge the WikiLeaks founder.

“The news that criminal charges have apparently been filed against Mr. Assange is even more troubling than the haphazard manner in which that information has been revealed,” Pollack said in a statement. “The government bringing criminal charges against someone for publishing truthful information is a dangerous path for a democracy to take.”

In a statement Friday the director of the American Civil Liberties Union’s Speech, Privacy, and Technology Project, Ben Wizner, seemed to agree.

"Any prosecution of Mr. Assange for Wikileaks’ publishing operations would be unprecedented and unconstitutional, and would open the door to criminal investigations of other news organizations," he said. "Moreover, prosecuting a foreign publisher for violating U.S. secrecy laws would set an especially dangerous precedent for U.S. journalists, who routinely violate foreign secrecy laws to deliver information vital to the public's interest."

Mueller has been investigating whether anyone close to President Trump’s 2016 campaign, including his longtime associate Roger Stone, acted as a conduit of stolen emails between WikiLeaks and the campaign.

WikiLeaks communicated through Twitter with the president’s son, Donald Trump Jr.

Assange came to prominence after WikiLeaks published secret military and diplomatic documents leaked in 2010 by Pvt. Chelsea Manning.

Manning served 7 years in prison, but WikiLeaks was not prosecuted. Justice Department lawyers concluded at the time that they could not charge Assange and WikiLeaks even as American newspapers, protected by the First Amendment, were publishing the leaked material.

But in recent years, U.S. officials have sought to distinguish WikiLeaks from journalists, as when then-CIA Director Mike Pompeo referred to it as a "hostile non-state intelligence organization." American officials came to view WikiLeaks as working hand in glove with American adversaries, particularly Russia.

In 2017, WikiLeaks published information about CIA hacking exploits, and last year a former government software engineer was charged with leaking that information. Officials said the disclosures were damaging to U.S. national security, and computer security experts criticized WikiLeaks for providing criminal hackers with new tools.

Assange, an Australian national, has lived at the Ecuadorean Embassy in London since being granted asylum in 2012 as he tried to avoid extradition to Sweden. Sweden's top prosecutor later dropped a long-running inquiry into a rape allegation against him, saying there was no way to detain or charge him because of his protected status in the embassy.

In a recent lawsuit, Assange said that Ecuador is changing the terms of his protection there.

CORRECTION (Nov. 15, 2018, 2:45 a.m. ET): An earlier version of this article misstated where Julian Assange is currently living. He is in the Ecuadorean Embassy in London, not Ecuador.