This week, we have our first The War Within Dungeon Event, awarding extra loot from normal, heroic, and base Mythic dungeons, as well as a Heroic Cache of Nerubian Treasures for completing the weekly quest!
Although the updated quest states that dungeons may be completed on Heroic difficulty, prior expansion dungeons like Siege of Boralus don't give credit.
While the extra loot from the final dungeon boss is not available on Mythic+, they can still be completed for the weekly quest cache, while players who are interested in normal, heroic, or base Mythic gear will find themselves looting more of it throughout the the week.
This is especially relevant to anyone completing base Mythic dungeons, as the change to a daily lockout means they are much more farmable over the course of the week.
Don't forget, though, that with the dungeon difficulty squish, base Mythic dungeons are also harder than they were in the past, so if you're new to completing dungeons in The War Within, prepare accordingly! Note that while the Sign of the Warrior buff applied this week is the same as last expansion and still references Dragonflight, those dungeons do not give credit for the quest.