The US government has filed sealed charges against WikiLeaks founder Julian Assange, the Washington Post’s Matt Zapotosky and Devlin Barrett confirmed Thursday.

The specifics of the charges aren’t yet known. The news only became public now due to a government slip-up: an unrelated legal filing contained references to sealing charges against Assange, apparently because of a cut-and-paste error. Seamus Hughes flagged the filing on Twitter, spurring the Post reporters to confirm the information.

Assange remains holed up in the Ecuadorian Embassy in London, where he has resided for six years in an attempt to avoid extradition. But his relationship with his hosts has frayed, and there are some indications that he may lose their protection soon.

Over the past decade, WikiLeaks has posted a plethora of leaked material from the State Department, the US military, the CIA, and various corporations — and emails from the DNC and John Podesta that were stolen by Russian government hackers.

So far, there’s no indication that the Assange charges are part of special counsel Robert Mueller’s probe. (The errant government filing mentioning him was from another office, the US Attorney’s Office for the Eastern District of Virginia.)

And it’s not clear which of WikiLeaks’ document dumps, if any, the charges against Assange relate to, or what law he’s been accused of breaking. That’s tremendously important because there have long been serious concerns about what prosecuting WikiLeaks’ founder for publishing stolen information would mean for freedom of the press.

Who is Julian Assange?

Assange is an Australian “hacktivist” who founded WikiLeaks in 2006, with the stated goal of publishing information the powerful were trying to keep secret. The group had its greatest successes in obtaining and posting US military, national security, and foreign policy documents, and Assange was a harsh critic of what he deemed the US’s imperialist ambitions.

Starting in 2010, WikiLeaks published a video of an airstrike in Iraq that killed civilians, military documents about the Iraq and Afghanistan wars, and State Department cables in which diplomats gave candid assessments of foreign governments — all provided by US Army Pvt. Chelsea Manning. The unprecedented leaks gained enormous attention and made Assange a sort of celebrity — and a target, as top US officials like Attorney General Eric Holder publicly mused about how they could charge him.

So in June 2012, Assange, a citizen of Australia who had lived abroad for several years, showed up at the Ecuadorian Embassy in London and asked for political asylum. His imminent danger was extradition to Sweden, where authorities were investigating a rape allegation against him. But Assange’s pitch was that he truly needed asylum from the United States, because of WikiLeaks’ work. The Ecuadorian government granted his request, and he’s been holed up inside the embassy ever since — for more than six years now.

In that time, WikiLeaks has continued to post new material — and grown more controversial. Assange roiled the 2016 presidential campaign by posting hacked emails from, first, the Democratic National Committee and then Clinton campaign chair John Podesta. (Mueller has since charged several Russian intelligence officers with carrying out these hacks.)

Was Assange simply bringing more transparency by publishing powerful people’s communications? Was he effectively just helping out the Russians and Donald Trump? Was he engaged in a project to weaken the US politically? Perhaps it was all of the above. (“We believe it would be much better for GOP to win,” Assange wrote privately in late 2015, according to messages obtained by the Intercept. Hillary Clinton, he continued, was “a bright, well connected, sadistic sociopath.”)

But Assange’s leaks didn’t stop once Trump was elected. In early 2017, WikiLeaks posted a new set of material about the CIA’s hacking capabilities, in a leak referred to as “Vault 7.” The New York Times wrote that this “appeared to be the largest leak of CIA documents in history,” and a former CIA software engineer, Joshua Schulte, has been charged in connection with it.

How did we learn that Julian Assange had been charged?

Top US officials have explored charging Assange for many years, but no action ended up being taken during the Obama administration. Shortly after the Vault 7 leak in early 2017, though, CNN reported that charges against Assange had been “prepared.”

Then the discussion was revived this Thursday, when the Wall Street Journal’s Aruna Viswanatha and Ryan Dube reported that the Justice Department “is preparing to prosecute” Assange and is “increasingly optimistic it will be able to get him into a US courtroom” — suggesting, perhaps, that Ecuador might withdraw their protection of him so he could be extradited.

But in a twist, the Journal piece spurred Seamus Hughes to point out on Twitter that there were odd, seemingly errant mentions of Assange in recent court filings for an unrelated case.

The filing, from an assistant US attorney for the Eastern District of Virginia in August, is about why a criminal complaint and arrest warrant against someone else should be sealed. But then it starts talking about why charges against Assange should be sealed:

Another procedure short of sealing will not adequately protect the needs of law enforcement at this time because, 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. … The complaint, supporting affidavit, and arrest warrant, as well as this motion and the proposed order, 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.

The mistake seemed likely to have been due to cutting and pasting language from an earlier, similar document that was about Assange.

So Washington Post reporters Matt Zapotosky and Devlin Barrett asked about what happened — and were told by “people familiar with the matter” that, yes, Assange had in fact been charged under seal (and that the court filing disclosure was “unintentional”).

What are the charges against Assange about?

We don’t know. And it’s really important.

The US government has already charged people whom they’ve accused of leaking classified information to WikiLeaks, like Manning and Schulte. But charging Assange or WikiLeaks solely for publishing such information is a more troubling thing to do, due to its implications for freedom of the press.

“Never in the history of this country has a publisher been prosecuted for presenting truthful information to the public,” the American Civil Liberties Union’s Ben Wizner told CNN last year. “Any prosecution of WikiLeaks for publishing government secrets would set a dangerous precedent that the Trump administration would surely use to target other news organizations.”

Indeed, many journalists often publish important and newsworthy stories based on leaked classified information. This was one reason why the Obama Justice Department opted not to charge Assange — they called it a “New York Times problem,” the Washington Post’s Sari Horwitz reported in 2013.

“If the Justice Department indicted Assange, it would also have to prosecute the New York Times and other news organizations and writers who published classified material, including The Washington Post and Britain’s Guardian newspaper,” Horwitz wrote, describing the officials’ conclusions.

However, it is possible that prosecutors are alleging that Assange’s conduct goes beyond simply receiving and publishing of stolen information — the Lawfare team and Marcy Wheeler have each floated various other possibilities. Depending on what exactly the government’s legal theory is, the implications for journalists could be enormous, or relatively minor.

We don’t even know which of the leaks, if any, the charges are about. It’s entirely possible that they pertain to the CIA hacking tool leaks (there’s been a lot of action in the prosecution of accused leaker Joshua Schulte lately), rather than the DNC or Podesta emails. To get a better idea, we’ll have to wait for the charges to be unsealed.