diff --git a/hang_emerge/init.lua b/hang_emerge/init.lua
index b24a753..3539ce1 100644
--- a/hang_emerge/init.lua
+++ b/hang_emerge/init.lua
@@ -1,3 +1,7 @@
+-- Calling minetest.emerge_area() with an out-of-bounds position like
+-- below makes Minetest 5.5 hang and waste CPU and RAM resources; any
+-- attacker could use it to hang a server. Note that x=32766 is safe.
+
 local emerge = function()
 	local i = 32767
 	minetest.emerge_area(