PaperMC/paper-server/nms-patches/net/minecraft/world/entity/projectile/EntityTippedArrow.patch

--- a/net/minecraft/world/entity/projectile/EntityTippedArrow.java
+++ b/net/minecraft/world/entity/projectile/EntityTippedArrow.java
@@ -118,7 +118,7 @@
                 mobeffect = (MobEffect) iterator.next();
                 entityliving.addEffect(new MobEffect(mobeffect.getEffect(), Math.max(mobeffect.mapDuration((i) -> {
                     return i / 8;
-                }), 1), mobeffect.getAmplifier(), mobeffect.isAmbient(), mobeffect.isVisible()), entity);
+                }), 1), mobeffect.getAmplifier(), mobeffect.isAmbient(), mobeffect.isVisible()), entity, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ARROW); // CraftBukkit
             }
         }
 
@@ -126,7 +126,7 @@
 
         while (iterator.hasNext()) {
             mobeffect = (MobEffect) iterator.next();
-            entityliving.addEffect(mobeffect, entity);
+            entityliving.addEffect(mobeffect, entity, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ARROW); // CraftBukkit
         }
 
     }