An unnamed client of Michael Cohen, President Donald Trump's longtime personal attorney, has been revealed as Fox News host Sean Hannity.
The revelation came after U.S. District Court judge Kimba Wood ordered Cohen's lawyer to disclose the name in a court hearing on Monday.
A lawyer for Cohen at the Monday hearing said that Cohen performed secret legal work for Hannity.
"We have been friends a long time. I have sought legal advice from Michael," Hannity said in response to being revealed as Cohen's third client, according to a Wall Street Journal reporter.
Hannity addressed the matter on his radio show Monday afternoon, and said in a statement on Twitter that Cohen has never represented him "in any matter."
He also said that he had "brief discussions" with Cohen about legal matters, but said he "assumed those conversations were confidential."
Less than an hour later, Hannity said in a separate statement that his legal discussions with Cohen were "almost exclusively about real estate."
"In response to some wild speculation, let me make clear that I did not ask Michael Cohen to bring this proceeding on my behalf, I have no personal interest in this proceeding, and, in fact, asked that my de minimis discussions with Michael Cohen, which dealt almost exclusively about real estate, not be made a part of this proceeding."
It is yet unclear what specific services Cohen provided for Hannity.
In an earlier court filing Monday morning, lawyers for Cohen refused to identify the recent client — one of three people Cohen represented between 2017 and 2018. The lawyers also refused to identify the names of other past clients.
Lawyers for Cohen — whose business records were seized by FBI agents April 9 — said the then-unnamed client had told Cohen not to disclose his name and that they believed Cohen had a duty not to disclose it.
They also said that if Cohen's clients, other than Trump, were publicly revealed, it is "likely to be embarrassing or detrimental to the client."
The lawyers added, "As to the one unnamed legal client, we do not believe that Mr. Cohen should be asked to reveal the name or can permissibly do so."
Fox News did not immediately respond to CNBC's request for comment.
A lawyer for Cohen said at the Monday hearing that he knows materials related to the Trump Organization were also seized during the raids of Cohen's home and office.
Cohen's other two clients were Trump and Elliott Broidy, a former Republican National Committee official who resigned following reports that he had impregnated a Playboy model in an extramarital affair. Cohen negotiated a payoff deal to the woman worth $1.6 million.
, the porn star who has said she was paid $130,000 by Cohen on the eve of the 2016 presidential election to keep quiet about her having sex with Trump in 2006, also attended the hearing.
Information about that payout was among the files seized from Cohen. Daniels is suing Trump in an attempt to void a nondisclosure agreement she signed about him. Trump was married to first lady Melania Trump at the time of the alleged affair.
Cohen's lawyers are seeking to bar prosecutors from getting first crack at reviewing a large number of files seized from Cohen's home, office, hotel room and more than a dozen electronic devices on April 9 by the FBI as part of an ongoing criminal investigation of him.
Cohen has not been charged, but prosecutors working for the U.S. Attorney's Office for the Southern District of New York reportedly are interested in the payoff to Daniels, Cohen's taxicab investments, and other business-related matters.
Files related to Daniels, whose real name is Stephanie Clifford, were among those seized.
Defense lawyers claim they, not a special "taint team" of prosecutors who will not be involved in the case, should get to identify which files should not be turned over to the actual prosecutors. They say doing so would violate Cohen's clients' rights to confidentiality with their attorney.
If Cohen's lawyers are not allowed to conduct the first review, they want a so-called special master, an appointed judge, to conduct it, before prosecutors get to see any of the files.
"If the government can obtain a search warrant for particular items but then seize and review everything in an attorney's office, the protections of the Fourth Amendment are meaningless," Cohen's lawyers wrote.
Trump's lawyer for the case, Joanna Hendon, on Sunday night told Wood in a letter that the president should get the first chance to review Cohen's files to decide which ones related to Trump are exempt from disclosure to prosecutors because of attorney-client privilege.
Prosecutors filed a brief in response to the president's claim that he should get first crack at reviewing Cohen's files. It says "the president's proposal would set a dangerous precedent."
A number of other previous clients are referred to in the Monday letter. The clients are not named. Cohen's lawyers said in their letter that they do not know if work for those clients was seized in the raids, or whether Cohen's work for them was relevant to the information sought by the search warrants authorizing the raids.
Cohen's attorneys also took a shot at prosecutors for having spied on his emails for some time before asking for permission to conduct the raids last week.
"To the extent it bears repeating, federal prosecutors have seized the data and files of the personal attorney of the President of the United States," the lawyers wrote.
This is completely unprecedented. Prior to the execution of the warrants at issue, prosecutors from the Southern District of New York had already intercepted emails from the President's personal lawyer. They apparently executed the search warrants at issue here only after they searched for private emails between the President of the United States and his personal lawyer and realized that 'zero emails were exchanged with President Trump.'
Rather than continue less intrusive investigative means, the USAO took the extraordinary step of raiding several locations, including Mr. Cohen's home, hotel room, and law office and took everything. This is perhaps the most highly publicized search warrant in the history of recent American criminal jurisprudence. It is paramount that the review of Mr. Cohen's data and documents be handled in such a way as to eliminate, as much as possible, even the 'appearance of unfairness.'
An earlier version of this story misstated who revealed Sean Hannity as Cohen's mystery client.
--CNBC's Jacob Pramuk contributed to this report.