--- a/net/minecraft/world/entity/monster/CaveSpider.java
+++ b/net/minecraft/world/entity/monster/CaveSpider.java
@@ -38,7 +_,7 @@
                 }
 
                 if (i > 0) {
-                    ((LivingEntity)source).addEffect(new MobEffectInstance(MobEffects.POISON, i * 20, 0), this);
+                    ((LivingEntity)source).addEffect(new MobEffectInstance(MobEffects.POISON, i * 20, 0), this, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ATTACK); // CraftBukkit
                 }
             }
 
