Fortnite Challenges will now start on Thursday, and this will be a permanent change for Challenges, with the Week 5 ones now available to unlock. One of these challenges is the "Follow the treasure map found in Greasy Grove", which will give you 10 stars.
The location of the chest is near Snobby Shores, so you'll want to head west first, and then land on top of the villain base. Hollowpoint has released a handy guide on YouTube to help you find the location more clearly. Check it out below: