--- a/net/minecraft/server/EntityCaveSpider.java
+++ b/net/minecraft/server/EntityCaveSpider.java
@@ -26,7 +26,7 @@
                 }
 
                 if (b0 > 0) {
-                    ((EntityLiving) entity).addEffect(new MobEffect(MobEffects.POISON, b0 * 20, 0));
+                    ((EntityLiving) entity).addEffect(new MobEffect(MobEffects.POISON, b0 * 20, 0), org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ATTACK); // CraftBukkit
                 }
             }