A collection of memos reportedly written by a former British intelligence agent and obtained by BuzzFeed allege that the Russian government cooperated with Donald Trump’s campaign to leak damaging information on Hillary Clinton and that Russia possessed compromising information about the president-elect’s financial interests and sexual activities in that country. A two-page synopsis of the dossier was given to Trump, President Obama, and eight congressional leaders last week in classified briefings presented by four U.S. intelligence chiefs, CNN reported on Tuesday. The Guardian also reports that the FBI had applied for a warrant to monitor “four members of the Trump team suspected of irregular contacts with Russian officials.” The Foreign Intelligence Surveillance Court initially turned down the application, but it’s not clear if it was eventually granted.

Nothing in the memos has been confirmed, and even their provenance is murky. According to the dossier, the Kremlin had been feeding Trump compromising information on his opponents for years. It had also acquired compromising information on Trump himself that could be used as blackmail. There are allegations of “perverted” sex acts and also of frequent contact between Trump’s campaign and Russian government intermediaries. Leaking of all kinds is alleged.

Update, 8:26 p.m.: Trump denies:

FAKE NEWS - A TOTAL POLITICAL WITCH HUNT! — Donald J. Trump (@realDonaldTrump) January 11, 2017

Among other things, the memos allege that Michael Cohen, a lawyer for Trump, met in Prague with Kremlin representatives in August 2016 at a time when the Trump campaign’s Russia ties were receiving negative publicity. Cohen on Tuesday fully denied the allegations, calling them “ridiculous on so many levels.” Cohen figures extensively in the memos, as does Trump foreign policy adviser Carter Page and former Trump campaign chairman Paul Manafort. (And don’t miss the cameos from Green Party candidate Jill Stein and fringe fixture Lyndon LaRouche.)

According to CNN, the memos are the work of a former agent of Britain’s MI6 who now runs a private intelligence firm. His work was initially reported on by David Corn of Mother Jones in October. The ex-spy’s research on Trump was first funded by rival Republican groups during the GOP primary, according to CNN, and then by groups supporting Hillary Clinton during the general election. We still don’t know who this agent is, who his sources are, how much credibility he has, or to what extent U.S. intelligence officials actually believe his claims. As BuzzFeed notes, the documents contain several misspellings and minor factual errors. But according to CNN, U.S. intelligence agencies recently deemed “his sources to be credible enough to include some of the information in the presentations to the President and President-elect a few days ago.”

This was apparently not the case before Election Day. CNN says some of the memos were “circulating as far back as last summer,” though it’s not clear how widely. The New York Times, in its wised-up way, reports that the details were “widely known among journalists and politicians in Washington” in the fall. In October, some of the memos, dated June through August, were provided by the agent to an FBI official. At least some of the allegations were included in classified briefings presented to congressional leaders last year, which prompted then–Senate Democratic Minority Leader Harry Reid to write to FBI Director James Comey in October, demanding a full investigation. In December, Sen. John McCain—who, per CNN, had received a full copy from a former British diplomat—passed it along to Comey. Tuesday’s stories will likely reopen questions about why the FBI chose to tell Congress about its investigation into Hillary Clinton’s handling of her emails rather than, well, any of this.

This post has been updated since publication.