Buried roughly in the middle of the Mueller report: Evidence that the Trump White House was receiving highly sensitive information about the U.S. targets of the FBI’s investigation into Russian election interference very early on, with Republican “Gang of Eight” member Sen. Richard Burr leaking all five major Trump-linked targets of the investigation to the White House almost immediately after receiving an FBI briefing on those targets.
On March 9, 2017, Comey briefed the "Gang of Eight" congressional leaders about the FBI's investigation of Russian interference, including an identification of the principal U.S. subjects of the investigation. Although it is unclear whether the President knew of that briefing at the time, notes taken by Annie Donaldson, then McGahn's chief of staff, on March 12, 2017, state, "POTUS in panic/chaos ... Need binders to put in front of POTUS. (1) All things related to Russia." The week after Comey's briefing, the White House Counsel's Office was in contact with SSCI Chairman Senator Richard Burr about the Russia investigations and appears to have received information about the status of the FBI investigation.
In a footnote, the report says that the "White House Counsel's Office was briefed by Senator Burr on the existence of '4-5 targets.'" From notes taken by Donaldson, those targets were Flynn ("DOJ looking for phone records"), Comey, Manafort, Carter Page, and "'Greek Guy' (potentially referring to George Papadopoulos, later charged with violating 18 USC 1000 for lying to the FBI)."
Those were indeed the five Trump campaign and administration targets whose actions would become a cornerstone into the investigation into collusion between Russian government efforts to undermine the U.S. election and potential Trump campaign connections to those acts.
That seems to be a shocking new development: Only months after Trump's inauguration, Sen. Richard Burr used his position as Gang of Eight member to inform the Trump White House of just which members of Trump's own inner circle were the identified "targets" of the FBI’s Russia investigation—just as that criminal and counterintelligence investigation was getting off the ground.