The Times is trying to make this a "new allegation" but it was brought up back during the confirmation hearings. The allegation is that he had his pants down and someone else pushed his penis into the hand of a woman at the party. Here's an
article from last October, during the confirmation hearings:
Guess what? The eyewitness denied it:
So a woman who wasn't sure it was Kavanaugh is backed up by a hearsay witness whose source denies any memory of the incident, but whose claim was nevertheless given credibility in the New York Times because they had nothing better to go with.
Apparently the new part of this story is that another classmate, Max Stier, has come forward to corroborate the story. Stier is getting a lot of boosting in the media as a straight-shooter, which raises the question: Where was he last year? Looking at the bio in this
article it's apparent he wasn't on some desert isle: