The latest - and perhaps most headline-grabbing - source of tension between Donald Trump and the US intelligence community is an unverified report, apparently compiled by a private intelligence firm, claiming Russia has gathered compromising data about the president-elect.
Those claims raise far more questions than they answer. Here is a summary of what we know so far.
Who wrote the report and why?
It has been widely attributed to Christopher Steele, a retired British intelligence officer.
Mr Steele, who runs a London-based intelligence firm, was reportedly hired by anti-Trump Republicans to investigate Mr Trump's ties to Russia during the battle for the party's presidential nomination. In the general election campaign the research was funded by an anonymous Democratic donor.
But since Mr Steele has been in hiding since the report surfaced on Tuesday, there is no confirmation that he is the author.
What does the report say?
It consists of a series of memos dated from June to December, and said to be based on information from members of the Russian intelligence community.
It claims that Russian officials have cultivated Mr Trump for at least five years to encourage splits within the Western alliance, and shared intelligence information with him.
Most startlingly, it alleges that Russia has managed to compromise Mr Trump and is in a position to blackmail him. It says Russia's FSB agency has footage of the president-elect using prostitutes at the Ritz-Carlton hotel in Moscow.
How did the public learn of the existence of the report?
CNN reported its existence on 10 January, and the Buzzfeed website published it in full.
How credible is the information it contains?
Since the report was published, Mr Trump has denounced it as "false and fictitious" and "made up, phony facts". Russian officials have also dismissed it as "pulp fiction".
All major media outlets have stressed that the report's allegations are unsubstantiated. Several, including the BBC, had knowledge of the claims before the election but were unable to verify them and therefore did not publish stories.
Newsweek says it "contains lots of Kremlin-related gossip" and points to factual errors and the misspelling of Russian names.
However, the reports were considered credible enough by the US intelligence community for a two-page summary to be given to both President Barack Obama and President-elect Trump in early January.
US Director of National Intelligence James Clapper has merely said the claims were still being assessed. He also strongly denied suggestions by Mr Trump that US intelligence agencies had been involved in leaking the report.