https://www.gamespot.com/articles/destiny-2-weekly-reset-malfeasance-is-out-ascendan/1100-6462028/

When playing Gambit, a special Primeval can now spawn in that drops an item called the Seething Heart. This leads to a series of quest steps (some of them quite difficult) that ultimately results in the acquisition of the Exotic hand cannon Malfeasance.