Paper/paper-server/nms-patches/net/minecraft/world/entity/monster/EntityCaveSpider.patch

--- a/net/minecraft/world/entity/monster/EntityCaveSpider.java
+++ b/net/minecraft/world/entity/monster/EntityCaveSpider.java
@@ -40,7 +40,7 @@
                 }
 
                 if (b0 > 0) {
-                    ((EntityLiving) entity).addEffect(new MobEffect(MobEffects.POISON, b0 * 20, 0), this);
+                    ((EntityLiving) entity).addEffect(new MobEffect(MobEffects.POISON, b0 * 20, 0), this, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ATTACK); // CraftBukkit
                 }
             }