fix(Core/XP): Reduce XP when ungrouped high-level player helps kill (#25161)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Ludwig <sudlud@users.noreply.github.com>

src/server/game/Entities/Creature/Creature.cpp

@@ -264,7 +264,7 @@ Creature::Creature(): Unit(), MovableMapObject(), m_groupLootTimer(0), lootingGr
     m_spawnId(0), m_equipmentId(0), m_originalEquipmentId(0), m_alreadyCallForHelp(false), m_AlreadyCallAssistance(false),
     m_AlreadySearchedAssistance(false), m_regenHealth(true), m_regenPower(true), m_AI_locked(false), m_meleeDamageSchoolMask(SPELL_SCHOOL_MASK_NORMAL), m_originalEntry(0), _gossipMenuId(0), m_moveInLineOfSightDisabled(false), m_moveInLineOfSightStrictlyDisabled(false),
     m_homePosition(), m_transportHomePosition(), m_creatureInfo(nullptr), m_creatureData(nullptr), m_detectionDistance(20.0f),_sparringPct(0.0f), m_waypointID(0), m_path_id(0), m_formation(nullptr), m_lastLeashExtensionTime(nullptr),
-    _isMissingSwimmingFlagOutOfCombat(false), m_assistanceTimer(0), _playerDamageReq(0), _damagedByPlayer(false), _isCombatMovementAllowed(true)
+    _isMissingSwimmingFlagOutOfCombat(false), m_assistanceTimer(0), _playerDamageReq(0), _damagedByPlayer(false), _highestPlayerAttackerLevel(0), _isCombatMovementAllowed(true)
 {
     m_regenTimer = CREATURE_REGEN_INTERVAL;
     m_valuesCount = UNIT_END;
@@ -3836,7 +3836,7 @@ bool Creature::IsDamageEnoughForLootingAndReward() const
     return m_creatureInfo->HasFlagsExtra(CREATURE_FLAG_EXTRA_NO_PLAYER_DAMAGE_REQ) || (_playerDamageReq == 0 && _damagedByPlayer);
 }
 
-void Creature::LowerPlayerDamageReq(uint32 unDamage, bool damagedByPlayer /*= true*/)
+void Creature::LowerPlayerDamageReq(uint32 unDamage, bool damagedByPlayer /*= true*/, uint8 attackerLevel /*= 0*/)
 {
     if (_playerDamageReq)
         _playerDamageReq > unDamage ? _playerDamageReq -= unDamage : _playerDamageReq = 0;
@@ -3845,12 +3845,16 @@ void Creature::LowerPlayerDamageReq(uint32 unDamage, bool damagedByPlayer /*= tr
     {
         _damagedByPlayer = damagedByPlayer;
     }
+
+    if (attackerLevel > _highestPlayerAttackerLevel)
+        _highestPlayerAttackerLevel = attackerLevel;
 }
 
 void Creature::ResetPlayerDamageReq()
 {
     _playerDamageReq = GetHealth() / 2;
     _damagedByPlayer = false;
+    _highestPlayerAttackerLevel = 0;
 }
 
 uint32 Creature::GetPlayerDamageReq() const

src/server/game/Entities/Creature/Creature.h

@@ -380,9 +380,10 @@ public:
     void SetLootRewardDisabled(bool disable) { DisableLootReward = disable; }
     [[nodiscard]] bool IsLootRewardDisabled() const { return DisableLootReward; }
     [[nodiscard]] bool IsDamageEnoughForLootingAndReward() const;
-    void LowerPlayerDamageReq(uint32 unDamage, bool damagedByPlayer = true);
+    void LowerPlayerDamageReq(uint32 unDamage, bool damagedByPlayer = true, uint8 attackerLevel = 0);
     void ResetPlayerDamageReq();
     [[nodiscard]] uint32 GetPlayerDamageReq() const;
+    [[nodiscard]] uint8 GetHighestPlayerAttackerLevel() const { return _highestPlayerAttackerLevel; }
 
     [[nodiscard]] uint32 GetOriginalEntry() const { return m_originalEntry; }
     void SetOriginalEntry(uint32 entry) { m_originalEntry = entry; }
@@ -554,6 +555,7 @@ private:
 
     uint32 _playerDamageReq;
     bool _damagedByPlayer;
+    uint8 _highestPlayerAttackerLevel;
     bool _isCombatMovementAllowed;
 };
 

src/server/game/Entities/Player/KillRewarder.cpp

@@ -16,6 +16,7 @@
  */
 
 #include "KillRewarder.h"
+#include "Creature.h"
 #include "Formulas.h"
 #include "Group.h"
 #include "Pet.h"
@@ -161,6 +162,19 @@ void KillRewarder::_RewardXP(Player* player, float rate)
         else
             xp = 0;
     }
+
+    // An ungrouped helper who out-levels everyone eligible for the kill and for
+    // whom the victim is gray halves the tagger's XP, matching the group
+    // gray-member penalty. Closes a power-leveling exploit.
+    if (xp)
+        if (Creature* creature = _victim->ToCreature())
+        {
+            uint8 const referenceLevel = _group ? _maxLevel : player->GetLevel();
+            uint8 const highestLevel = creature->GetHighestPlayerAttackerLevel();
+            if (highestLevel > referenceLevel && creature->GetLevel() <= Acore::XP::GetGrayLevel(highestLevel))
+                xp = xp / 2 + 1;
+        }
+
     if (xp)
     {
         // 4.2.2. Apply auras modifying rewarded XP (SPELL_AURA_MOD_XP_PCT).

src/server/game/Entities/Unit/Unit.cpp

@@ -1233,7 +1233,18 @@ uint32 Unit::DealDamage(Unit* attacker, Unit* victim, uint32 damage, CleanDamage
             uint32 unDamage = health < damage ? health : damage;
             bool damagedByPlayer = unDamage && attacker && (attacker->IsPlayer() || attacker->m_movedByPlayer != nullptr
                 || attacker->GetCharmerGUID().IsPlayer());
-            victim->ToCreature()->LowerPlayerDamageReq(unDamage, damagedByPlayer);
+
+            uint8 attackerLevel = 0;
+            if (damagedByPlayer)
+            {
+                Player* attackerPlayer = attacker->GetCharmerOrOwnerPlayerOrPlayerItself();
+                if (!attackerPlayer && attacker->m_movedByPlayer)
+                    attackerPlayer = attacker->m_movedByPlayer->ToPlayer();
+                if (attackerPlayer)
+                    attackerLevel = attackerPlayer->GetLevel();
+            }
+
+            victim->ToCreature()->LowerPlayerDamageReq(unDamage, damagedByPlayer, attackerLevel);
         }
     }