This secret challenge came with Fortnite update 12.30. It most certainly announces a broader event that will take place in the coming weeks. It's divided into two parts, and will first ask you to receive your orders at Bear HQ, before leaving in search of five jars of honey.
Completing this challenge will reward you with 40,000 XP, same as for a classic challenge.
Step 1: find the bears' plans
Before searching for the honey pots, you'll need to activate your quest by going to Bear HQ. This is located in the northwest corner of Weeping Woods. Specifically, it's located behind a secret tunnel in the library.
Interact with the cabinet, then go through the secret hatch, destroy the metal shutter, and you're in the heart of the ursine operational base! Make your way to the central office, where teddy bears are gathered. The planisphere on the wall should activate. This is where your quest for the honeypots begins!
Honey Map
1st Jar of Honey: In the orchards of Frenzy Farm
The first honey pot is in the orchards just north of Frenzy Farm. Against an apple tree you'll find the first jar of honey.
2nd Jar of Honey: Northeast of Holly Hedges
This jar is also placed against a tree, this time near a pond.
3rd Jar of Honey: In the south of the Agency
This jar is on the heights south of the Agency. It dominates Midas lair. Beware of landing near this disputed spawn!
4th Jar of Honey: South East of Frenzy Farm
This jar is at the foot of a huge apple tree.
5th Jar of Honey: North of Pleasant Park
The very last pot is next to the isolated houses, north of Pleasant Park.
Alongside the battle between Shadow and Ghost, there are new secret challenges dealing with gnomes and bears. For this one, you'll have to find garden gnomes and telescopes.
