# UNDF: UNDF-2026-000000937
--- a/src/surroundings_menu.cpp
+++ b/src/surroundings_menu.cpp
@@ -1,5 +1,6 @@
 // ... (includes)
 #include <algorithm>
+#include <unordered_set>

 // In item_tab_data::add_item_recursive()
 // BEFORE (CWE-407): item_order is std::vector<std::string> with std::find
@@ -241,7 +242,8 @@
 void item_tab_data::add_item_recursive( std::vector<std::string> &item_order, const item *it,
                                         const tripoint_rel_ms &relative_pos )
 {
+    // Also pass item_order_set for O(1) membership check
     const std::string name = it->tname();

-    if( std::find( item_order.begin(), item_order.end(), name ) == item_order.end() ) {
+    if( item_order_set.find( name ) == item_order_set.end() ) {
         item_order.push_back( name );
+        item_order_set.insert( name );

         items[name] = map_entity_stack<item>( it, relative_pos, it->count() );
     } else {
@@ -259,6 +261,7 @@
 void item_tab_data::find_nearby_items( const Character &you, map &m )
 {
     std::vector<std::string> item_order;
+    // Add std::unordered_set<std::string> item_order_set as class member

 // Similarly in terfurn_tab_data::add_terfurn()
 // BEFORE:
@@ -585,7 +588,8 @@
 void terfurn_tab_data::add_terfurn( std::vector<std::string> &item_order,
                                     const map_data_common_t *terfurn, const tripoint_rel_ms &relative_pos )
 {
     const std::string name = terfurn->name();

-    if( std::find( item_order.begin(), item_order.end(), name ) == item_order.end() ) {
+    if( item_order_set.find( name ) == item_order_set.end() ) {
         item_order.push_back( name );
+        item_order_set.insert( name );

         terfurns[name] = map_entity_stack<map_data_common_t>( terfurn, relative_pos );
     } else {