Trump is alleged to have made some promise, to an unnamed foreign leader, that was so disturbing that it 1. prompted a member of the intelligence community to file a whistleblower report that the intelligence community's IG found to be a credible report on an urgent matter and 2. that the Trump admin appears to have tried to cover up, by refusing to notify congressional intelligence committees about the complaint and forwarding it in full.

WaPo story (since corroborated by NBC reporter):

Vox summary:

JustSecurity discussion arguing that the attempted cover-up is illegal: https://www.nationalsecuritylawpodca...eeds-a-reboot/

Not long ago, reports emerged of a phone call between Trump and a senior Chinese official, in which he was reported to have promised Xi Jinping the US would not condemn China in the event of a violent crackdown on protests in Hong Kong:

This story was promptly drowned out by the deluge of asinine reporting on the Greenland story. If the whistleblower report is about an unrelated matter (which is likely - former insiders are speculating that it would have to be about something outright illegal or so grossly outrageous that it cannot be kept hidden, for the ICIG to make the determination he made), you've gotta wonder how many foreign leaders POTUS has been going around making dodgy promises to. Genuinely concerning that the president would engage in such dodgy conduct, and that an American administration would go to such great lengths to cover it up.