Paper/paper-server/nms-patches/net/minecraft/world/item/ItemMilkBucket.patch

--- a/net/minecraft/world/item/ItemMilkBucket.java
+++ b/net/minecraft/world/item/ItemMilkBucket.java
@@ -29,7 +29,7 @@
         }
 
         if (!world.isClientSide) {
-            entityliving.removeAllEffects();
+            entityliving.removeAllEffects(org.bukkit.event.entity.EntityPotionEffectEvent.Cause.MILK); // CraftBukkit
         }
 
         return itemstack.isEmpty() ? new ItemStack(Items.BUCKET) : itemstack;