It shouldn't be possible to bubble or stealth with WSG flag.

In classic you get an error message and it doesn't let you cast it, instead of casting it and causing flag to drop. The attribute that I believe controls this was only added to immunity spells in patch 1.9, so that would indicate it was possible to bop people to make them drop flag in early vanilla.

src/game/Objects/Unit.cpp

@@ -5506,37 +5506,31 @@ bool Unit::IsImmuneToSpell(SpellEntry const* spellInfo, bool /*castOnSelf*/) con
         spellInfo->HasAttribute(SPELL_ATTR_EX3_IGNORE_CASTER_AND_TARGET_RESTRICTIONS))
         return false;
 
-    //TODO add spellEffect immunity checks!, player with flag in bg is immune to immunity buffs from other friendly players!
-    //SpellImmuneList const& dispelList = m_spellImmune[IMMUNITY_EFFECT];
-
-    SpellImmuneList const& dispelList = m_spellImmune[IMMUNITY_DISPEL];
-    for (const auto& itr : dispelList)
+    // Venomhide Ravasaur (6508) is immune to being poisoned by others, but has passive poison aura 14108.
+    // Should either check self cast or passive spell here, not sure which is better.
+    if (!spellInfo->HasAttribute(SPELL_ATTR_PASSIVE))
     {
-        if (itr.type == spellInfo->Dispel)
+        SpellImmuneList const& dispelList = m_spellImmune[IMMUNITY_DISPEL];
+        for (const auto& itr : dispelList)
         {
-            SpellEntry const* pImmunitySpell = sSpellMgr.GetSpellEntry(itr.spellId);
-
-            if (!pImmunitySpell)
+            if (itr.type == spellInfo->Dispel)
             {
-                // Venomhide Ravasaur (6508) is immune to being poisoned by others, but has passive poison aura 14108.
-                // Should either check self cast or passive spell here, not sure which is better.
-                if (spellInfo->IsPassiveSpell())
-                    continue;
-
-                return true;
-            }
+                SpellEntry const* pImmunitySpell = sSpellMgr.GetSpellEntry(itr.spellId);
+                if (!pImmunitySpell)
+                    return true;
 
-            if ((pImmunitySpell->IsPositiveSpell()) != spellInfo->IsPositiveSpell())
-                return true;
+                if ((pImmunitySpell->IsPositiveSpell()) != spellInfo->IsPositiveSpell())
+                    return true;
 
-            if (pImmunitySpell->HasAttribute(SPELL_ATTR_EX_IMMUNITY_TO_HOSTILE_AND_FRIENDLY_EFFECTS))
-                return true;
+                if (pImmunitySpell->HasAttribute(SPELL_ATTR_EX_IMMUNITY_TO_HOSTILE_AND_FRIENDLY_EFFECTS))
+                    return true;
+            }
         }
     }
 
-    if (!(spellInfo->Attributes & SPELL_ATTR_NO_IMMUNITIES)               // ignore invulnerability
-     && !(spellInfo->AttributesEx & SPELL_ATTR_EX_IMMUNITY_PURGES_EFFECT) // can remove immune (by dispell or immune it)
-     && !(spellInfo->AttributesEx2 & SPELL_ATTR_EX2_NO_SCHOOL_IMMUNITIES))
+    if (!spellInfo->HasAttribute(SPELL_ATTR_NO_IMMUNITIES)             // ignore invulnerability
+     && !spellInfo->HasAttribute(SPELL_ATTR_EX_IMMUNITY_PURGES_EFFECT) // can remove immune (by dispell or immune it)
+     && !spellInfo->HasAttribute(SPELL_ATTR_EX2_NO_SCHOOL_IMMUNITIES))
     {
         SpellImmuneList const& schoolList = m_spellImmune[IMMUNITY_SCHOOL];
         for (const auto& itr : schoolList)
@@ -5592,6 +5586,41 @@ bool Unit::IsImmuneToSpell(SpellEntry const* spellInfo, bool /*castOnSelf*/) con
         }
     }
 
+    // Spells with this attribute cant be cast if there is aura that will be removed by it.
+    // Example: Trying to stealth or bubble with WSG flag.
+    // Most immunity spells only received the attribute in patch 1.9.
+    if (spellInfo->HasAttribute(SPELL_ATTR_EX2_FAIL_ON_ALL_TARGETS_IMMUNE))
+    {
+        bool hasStealth = false;
+        bool hasImmunity = false;
+        for (auto const& auraType : spellInfo->EffectApplyAuraName)
+        {
+            switch (auraType)
+            {
+                case SPELL_AURA_MOD_STEALTH:
+                case SPELL_AURA_MOD_INVISIBILITY:
+                    hasStealth = true;
+                    break;
+                case SPELL_AURA_EFFECT_IMMUNITY:
+                case SPELL_AURA_SCHOOL_IMMUNITY:
+                    hasImmunity = true;
+                    break;
+            }
+        }
+
+        if (hasStealth || hasImmunity)
+        {
+            for (auto const& itr : m_spellAuraHolders)
+            {
+                SpellEntry const* pAuraSpell = itr.second->GetSpellProto();
+                if (hasStealth && pAuraSpell->HasAuraInterruptFlag(AURA_INTERRUPT_STEALTH_INVIS_CANCELS))
+                    return true;
+                if (hasImmunity && pAuraSpell->HasAuraInterruptFlag(AURA_INTERRUPT_INVULNERABILITY_BUFF_CANCELS))
+                    return true;
+            }
+        }
+    }
+
     return false;
 }