If you aren't familiar with the word "exfiltration" that's to be expected: It's the rare removal of an intelligence asset who is thought to be in imminent danger—and CNN reports one such exfiltration allegedly happened in 2017 in Russia. It reports one of America's "highest-level covert sources" inside the government there was pulled from the country in the secret mission, per "multiple Trump administration officials with direct knowledge." It's extremely light on details about the spy (to help safeguard the spy's identity, per CNN) and the extraction (details that CNN says it is not privy to). As such, the bulk of the report tries to get at the "why" behind the extraction, with some sources pointing a finger at the current administration's handling of classified material.
The report sees a correlation with President Trump's May 2017 White House meeting with Russian Foreign Minister Sergey Lavrov and then-Russian Ambassador to the US Sergey Kislyak, in which top-secret info on Syria was discussed. CNN writes, "The disclosure to the Russians by the President, though not about the Russian spy specifically, prompted intelligence officials to renew earlier discussions about the potential risk of exposure." The CIA calls the suggestion that Trump's handling of classified material forced an alleged exfiltration "inaccurate"; the White House pushed back as well. The Guardian reports the last time a US asset is known to have been pulled from Russia was in 2010, when Alexander Poteyev was exfiltrated; he is thought to now live in hiding in the US. (Read more spy stories.)