diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7df5492d..47abbcd8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,7 +12,7 @@
 
   * Add `Plug.Conn.get_session/3` for default value
   * Allow `Plug.SSL.configure/1` to accept all :ssl options
-  * Optimize query decoding by 15% to 45% - this removes the previously deprecated `:limit` MFA and `:include_unnamed_parts_at` from MULTIPART
+  * Optimize query decoding by 15% to 45% - this removes the previously deprecated `:limit` MFA and `:include_unnamed_parts_at` from MULTIPART. This may be backwards incompatible for applications that were relying on ambiguous arguments, such as `user[][key]=1&user[][key]=2`, which has unspecified parsing behaviour
 
 ## v1.14.2 (2023-03-23)
 
diff --git a/lib/plug/conn/query.ex b/lib/plug/conn/query.ex
index 8d7764c3..e7d9026a 100644
--- a/lib/plug/conn/query.ex
+++ b/lib/plug/conn/query.ex
@@ -24,6 +24,20 @@ defmodule Plug.Conn.Query do
       iex> decode("foo[]=bar&foo[]=baz")["foo"]
       ["bar", "baz"]
 
+  > #### Nesting inside lists {: .error}
+  >
+  > Nesting inside lists is ambiguous and unspecified behaviour.
+  > Therefore, you should not rely on the decoding behaviour of
+  > `user[][foo]=1&user[][bar]=2`.
+  >
+  > As an alternative, you can explicitly specify the keys:
+  >
+  >     # If foo and bar belong to the same entry
+  >     user[0][foo]=1&user[0][bar]=2
+  >
+  >     # If foo and bar are different entries
+  >     user[0][foo]=1&user[1][bar]=2
+
   Keys without values are treated as empty strings,
   according to https://url.spec.whatwg.org/#application/x-www-form-urlencoded: