Minecraft wiki entry for Multiplayer_PvP_bases, associated text: For ChestESP
The way ChestESP works is by detecting any chests around the hacker's viewpoint, a hack that can foil the x-ray defense. But, it can't detect dispensers, droppers, hoppers or anything that can store items. So, to protect against this, move everything you have in your chests into a storage compartment, anything above, or in your inventory. Ender chests are extremely helpful, as well. Obviously, this is not the best way to store things, so if you feel confident in your base's security, you may just want to risk leaving your stuff in your chests. Shulker boxes stored within dispensers or an ender chest is usually the best method.