I started getting this yesterday as well. All ad descriptions are coming up as a listing for a 1962 - 1974 Mopar B & E Body 3pt Black Retractable Seatbelt Replacement buckle from Welder Joe's in Slippery Gap, WA
Apparently that is a valid ebay user but even all his ads show this iframe hack.
I watch my browser go through the site addresses as it loads the screen. first its the ebaystatic ebayimg etc, then it hits thehoffmangroup.com, then acedux.com Seems to be where the hack comes through
Called ebay and they could care less.
See screenshot attached