Fortnite recently tweeted out that they had disabled the use of Shopping Carts due to an issue caused by them. There was no further information given as to what there issues were, but after searching on the FortniteBR Reddit, we know the issue that was being caused by the Shopping Carts.
Reddit user AyJayPeeTV provided clips of how players can use Shopping Carts to get underneath the map. By building ramps on the side of the map, you can then continue until you get to the centre of the map if you have enough materials to spare.
AyJay also provides a tip on how you can kill players abusing this bug
There’s been a handful of times where players have been able to get under the map and get easy wins, thankfully Epic acted quickly and disabled the use of Shopping Carts whilst finding a fix.