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
@@ -213,7 +213,7 @@
             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
         }
 
         if (!this.effects.isEmpty()) {
@@ -221,7 +221,7 @@
 
             while (iterator.hasNext()) {
                 mobeffect = (MobEffect) iterator.next();
-                entityliving.addEffect(mobeffect, entity);
+                entityliving.addEffect(mobeffect, entity, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ARROW); // CraftBukkit
             }
         }