A failtroll active around on the Ifunny, he's quite infamous on the app mostly for the video in which he cut up a rat and injected his Cum into it aswell as one where he coomed into a jar with an epstein figure in it.
He posts mostly offensive and dark Gif captions which would be whatever if not the rat video he made
He very likely has connections with Foodists or Order Of 9 Troons type groups but he himself doesn't seem to have intentions. Yet despite all of this a significant part of deep Ifunniers interacts with him
TLDR; His whole personality is being a degenerate and "larping" as a pedo, which isn't funny when you realize he isn't ironic.
Also he possibly made multiple accounts here though Snopes yet has to fact check if it was really him.
Another reason why he's very likely isn't ironic is because he ran a cord server in which minors we're doing pics similar to 'Cados coinslot which makes jeffstein even more of a slopjak.
What should you do if you see jeffstein?
Nothing.
He's an attention whore who likes when people are obsessed with him, this article exists so people would know who xe is and would avoid interacting with him.