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

--- a/net/minecraft/world/item/ItemPotion.java
+++ b/net/minecraft/world/item/ItemPotion.java
@@ -62,7 +62,7 @@
                 if (((MobEffectList) mobeffect.getEffect().value()).isInstantenous()) {
                     ((MobEffectList) mobeffect.getEffect().value()).applyInstantenousEffect(entityhuman, entityhuman, entityliving, mobeffect.getAmplifier(), 1.0D);
                 } else {
-                    entityliving.addEffect(mobeffect);
+                    entityliving.addEffect(mobeffect, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.POTION_DRINK); // CraftBukkit
                 }
 
             });