diff --git a/mods/MAPGEN/mcl_dungeons/init.lua b/mods/MAPGEN/mcl_dungeons/init.lua
index 82e73eeb51..f809b18e4e 100644
--- a/mods/MAPGEN/mcl_dungeons/init.lua
+++ b/mods/MAPGEN/mcl_dungeons/init.lua
@@ -139,7 +139,7 @@ local function ecb_spawn_dungeon(blockpos, action, calls_remaining, param)
 		for tz = z+1, z+dim.z do
 			local fdef = registered_nodes[get_node({x = tx, y = y_floor  , z = tz}).name]
 			local cdef = registered_nodes[get_node({x = tx, y = y_ceiling, z = tz}).name]
-			if not fdev or not fdev.walkable or not cdev or not cdev.walkable then return false end
+			if not fdef or not fdef.walkable or not cdef or not cdef.walkable then return false end
 		end
 		end
 	end
diff --git a/mods/TODO.CORE b/mods/TODO.CORE
new file mode 100644
index 0000000000..62d5ed1a4b
--- /dev/null
+++ b/mods/TODO.CORE
@@ -0,0 +1,16 @@
+CORE/_mcl_autogroup/init.lua:
+-> Enumerates entries of the registered_nodes table.  Safe.
+
+CORE/flowlib/init.lua:
+-> All instances are checked before use.
+
+CORE/mcl_explosions/init.lua:
+-> Enumerates entries of the registered_nodes table.  Safe.
+
+CORE/walkover/init.lua:
+-> Enumerates entries of the registered_nodes table.  Safe.
+
+CORE/mcl_util/init.lua:
+-> All instances are checked before use.
+- should use local.
+- defines mcl_util.call_on_rightclick, but does not use it.
diff --git a/mods/TODO.ENTITIES b/mods/TODO.ENTITIES
new file mode 100644
index 0000000000..9d1cdaf99b
--- /dev/null
+++ b/mods/TODO.ENTITIES
@@ -0,0 +1,61 @@
+ENTITIES/mcl_boats/init.lua:
+-> All instances are checked before use.
+- one use in stray comment.
+- should use local or should use mcl_util.call_on_rightclick.
+
+ENTITIES/mcl_dripping/init.lua:
+-> Only references one directly indexed entry. Safe.
+
+ENTITIES/mcl_mobs/api.lua:
+-> Uses node_ok() that checks and always returns valid nodes. Safe.
+- line 1331 minetest.registered_items?  Fixed
+- should use locals.
+
+ENTITIES/mcl_mobs/spawning.lua:
+-> Only instances in commented out spawning code. Safe.
+
+ENTITIES/mcl_mobs/mount.lua:
+-> All instances shielded by node_ok(). Safe.
+
+ENTITIES/mobs_mc/snowman.lua:
+-> All instances checked.  Safe.
+- line 107 belowdef.nod_box == nil ?
+
+ENTITIES/mobs_mc/2_throwing.lua:
+-> All instances checked.  Safe.
+
+ENTITIES/mobs_mc/3_shared.lua:
+-> Unchecked accesses. Fixed.
+
+ENTITIES/mobs_mc/enderman.lua:
+-> Unchecked accesses. Fixed.
+- line 69: use indexed registered_nodes.
+- line 259: weird but works.
+- line 409 and onwards: restricted to takable_nodes.
+
+ENTITIES/mobs_mc/blaze.lua:
+-> Unchecked access. Fixed.
+
+ENTITIES/mobs_mc/slime+magma_cube.lua:
+-> Unchecked accesses. Fixed.
+
+ENTITIES/mobs_mc/5_spawn_abm_check.lua:
+-> Does not appear to be used at all.
+- unchecked access.  Unfixed.
+
+ENTITIES/mcl_paintings/init.lua:
+-> All instances checked.  Safe.
+
+ENTITIES/mcl_item_entity/init.lua:
+-> Unchecked access.  Fixed.
+
+ENTITIES/mcl_falling_nodes/init.lua:
+-> All instances checked.  Safe.
+- line 170: minetest.registered_nodes[self.node.name] is the same as bcd set on line 155
+  because of condition on line 164, therefore this access is safe.  Sloppy code though.
+
+ENTITIES/mcl_minecarts/init.lua:
+-> Unchecked access.  Fixed.
+
+ENTITIES/mobs_mc_gameconfig/init.lua:
+-> Only explicit indexing of registered_nodes. Safe
diff --git a/mods/TODO.ITEMS b/mods/TODO.ITEMS
new file mode 100644
index 0000000000..4ebc07f848
--- /dev/null
+++ b/mods/TODO.ITEMS
@@ -0,0 +1,156 @@
+ITEMS/mcl_portals/portal_nether.lua
+-> not checked.
+ITEMS/mcl_portals/portal_gateway.lua
+-> not checked.
+ITEMS/mcl_portals/portal_end.lua
+-> not checked.
+ITEMS/mcl_sponges/init.lua
+-> not checked.
+ITEMS/mcl_beds/api.lua
+-> not checked.
+ITEMS/mcl_beds/functions.lua
+-> not checked.
+ITEMS/mcl_torches/api.lua
+-> not checked.
+ITEMS/mcl_tools/init.lua
+-> not checked.
+ITEMS/mcl_ocean/seagrass.lua
+-> not checked.
+ITEMS/mcl_ocean/kelp.lua
+-> not checked.
+ITEMS/mcl_ocean/corals.lua
+-> not checked.
+ITEMS/mcl_ocean/sea_pickle.lua
+-> not checked.
+ITEMS/mcl_lanterns/init.lua
+-> not checked.
+ITEMS/mcl_stairs/api.lua
+-> not checked.
+ITEMS/mcl_stairs/cornerstair.lua
+-> not checked.
+ITEMS/mcl_dye/init.lua
+-> not checked.
+ITEMS/mcl_bows/crossbow.lua
+-> not checked.
+ITEMS/mcl_bows/bow.lua
+-> not checked.
+ITEMS/mcl_bows/rocket.lua
+-> not checked.
+ITEMS/mcl_bows/arrow.lua
+-> not checked.
+ITEMS/mcl_buckets/init.lua
+-> not checked.
+ITEMS/mcl_buckets/register.lua
+-> not checked.
+ITEMS/mcl_throwing/register.lua
+-> not checked.
+ITEMS/mcl_flowers/init.lua
+-> not checked.
+ITEMS/mcl_tnt/init.lua
+-> not checked.
+ITEMS/mcl_cocoas/init.lua
+-> not checked.
+ITEMS/xpanes/init.lua
+-> not checked.
+ITEMS/mcl_potions/tipped_arrow.lua
+-> not checked.
+ITEMS/mcl_potions/potions.lua
+-> not checked.
+ITEMS/mcl_potions/init.lua
+-> not checked.
+ITEMS/mcl_end/end_crystal.lua
+-> not checked.
+ITEMS/mcl_end/chorus_plant.lua
+-> not checked.
+ITEMS/mcl_walls/init.lua
+-> not checked.
+ITEMS/mcl_fishing/init.lua
+-> not checked.
+ITEMS/mcl_composters/init.lua
+-> not checked.
+ITEMS/mcl_heads/init.lua
+-> not checked.
+ITEMS/mclx_fences/init.lua
+-> not checked.
+ITEMS/mcl_mobspawners/init.lua
+-> not checked.
+ITEMS/mclx_stairs/init.lua
+-> not checked.
+ITEMS/mclx_core/init.lua
+-> not checked.
+ITEMS/mcl_core/nodes_base.lua
+-> not checked.
+ITEMS/mcl_core/nodes_misc.lua
+-> not checked.
+ITEMS/mcl_core/nodes_cactuscane.lua
+-> not checked.
+ITEMS/mcl_core/nodes_climb.lua
+-> not checked.
+ITEMS/mcl_core/craftitems.lua
+-> not checked.
+
+ITEMS/mcl_core/functions.lua
+-> Unchecked accesses.  Fixed.
+
+ITEMS/mcl_fire/init.lua
+-> not checked.
+ITEMS/mcl_fire/fire_charge.lua
+-> not checked.
+ITEMS/mcl_fire/flint_and_steel.lua
+-> not checked.
+ITEMS/mcl_banners/init.lua
+-> not checked.
+ITEMS/mcl_farming/shared_functions.lua
+-> not checked.
+ITEMS/mcl_farming/hoes.lua
+-> not checked.
+ITEMS/mcl_farming/soil.lua
+-> not checked.
+ITEMS/mcl_signs/init.lua
+-> not checked.
+ITEMS/mcl_maps/init.lua
+-> not checked.
+ITEMS/screwdriver/init.lua
+-> not checked.
+ITEMS/mcl_nether/lava.lua
+-> not checked.
+ITEMS/mcl_nether/nether_wart.lua
+-> not checked.
+ITEMS/mcl_books/init.lua
+-> not checked.
+ITEMS/mcl_chests/init.lua
+-> not checked.
+ITEMS/mcl_hoppers/init.lua
+-> not checked.
+ITEMS/mcl_colorblocks/init.lua
+-> not checked.
+ITEMS/REDSTONE/mcl_dispensers/init.lua
+-> not checked.
+ITEMS/REDSTONE/mcl_droppers/init_new.lua
+-> not checked.
+ITEMS/REDSTONE/mcl_droppers/init.lua
+-> not checked.
+ITEMS/REDSTONE/mcl_comparators/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_pressureplates/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_walllever/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_button/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons/internal.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons/util.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_mvps/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_wires/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_delayer/init.lua
+-> not checked.
+ITEMS/REDSTONE/mesecons_pistons/init.lua
+-> not checked.
+ITEMS/mcl_itemframes/init.lua
+-> not checked.
+ITEMS/mcl_doors/api_doors.lua
+-> not checked.
diff --git a/mods/TODO.MAPGEN b/mods/TODO.MAPGEN
new file mode 100644
index 0000000000..0cba3f3464
--- /dev/null
+++ b/mods/TODO.MAPGEN
@@ -0,0 +1,17 @@
+MAPGEN/mcl_villages/buildings.lua
+-> Only use is checked.  Safe.
+
+MAPGEN/mcl_villages/utils.lua
+-> Only indexed uses.  Safe.
+
+MAPGEN/tsm_railcorridors/init.lua
+-> Unchecked accesses.  Fixed.
+
+MAPGEN/mcl_structures/init.lua
+-> Unchecked access. Fixed.
+
+MAPGEN/mcl_dungeons/init.lua
+-> Unchecked accesses.  Fixed.
+
+MAPGEN/mcl_mapgen_core/init.lua
+-> All uses are checked.  Safe.