The bug
The effect for entities swimming in lava ignores the height that the lava actually is. This means that if lava exists in the block space in any form, any entity that enters that block space will take lava damage (via soul sand, slabs, stairs, lanterns, jumping, etc.)
Linked issues
is duplicated by 5
MC-131634
Getting burnt if on top of non-full block
Resolved
MC-153184
player catches on fire when standing on top of soul sand that is adjacent to lava
Resolved
MC-166752
Mobs swim above height of lava slice instead of leaving lava
Resolved
MC-176246
Hitboxes of lava blocks
Resolved
MC-183218
Player set on fire by lava even if not touching it
Resolved
relates to 2
Attachments
Comments 4
Might be fixed in 20w14a, see MC-173192
Relates to MC-1448.