After swarming past the 1 million unit threshold, WWZ has been busy adding in new content, much like the Undead Sea patch released back in May.

Now in celebration of summer’s arrival, the Six Skull update goes beyond the previous Insane level cap, as the free update offers an Extreme difficulty level to test your skills in this action co-op shooter.

Focus Home Interactive commented on the newly released patch:

Aside from the additional mode, the patch also features a series of balance tweaks and new weapon unlocks, including the wakizashi melee weapon and new sniper rifle variant, which are earned by beating levels in Extreme mode.

One of those balance tweaks includes a change to ammo crates, with limited ammo available depending on the difficulty level selected, while a fan-requested change arrives as AI bots will no longer explode barrels and mines by accidental shooting. You can read the full patch notes over here.

World War Z’s free Six Skulls update is available now on the PS4 and Xbox One editions, with the update set to arrive soon for the Epic Games Store PC version.

Want to get started with World War Z but aren’t quite ready for Insane or Extreme modes yet? Check out our guide to the best campaign builds over here and give yourself an edge in the zombie killing mayhem.