https://www.gamespot.com/articles/destiny-2s-new-faction-rally-exploit-lets-you-earn/1100-6454755/

It's unclear if Bungie plans to patch this exploit, but it's still active as of this writing. One thing to bear in mind is that only the first 30 engrams you receive from a faction (per character) has a chance to offer item rewards. Beyond that point, you'll only receive shaders. Still, considering that the three factions are competing to earn the most rewards--which results in that faction's unique weapon being sold during Victory Week--players may be frustrated if the results are swung by players making use of the exploit.