Even though it is supposed to be invincible when fed a block, the Sulfur Cube introduced in this very snapshot (26.2-snapshot-1) still takes damage and even dies from fire damage like lava, as well as all kinds of harmful potion effects (Harming, Poison, Wither).
Steps to reproduce:
Summon a sulfur cube and feed it a block
Splash it with a harmful potion, light it on fire or push it into lava
Expected Result:
The Cube is immune to all sources of Damage.
Actual result:
It is not immune to potions and fire.
Its supposed to die from lava and fire but i am not sure about the potion.