diff --git a/doc/changes/8350.md b/doc/changes/8350.md
new file mode 100644
index 000000000000..afed7fb49e91
--- /dev/null
+++ b/doc/changes/8350.md
@@ -0,0 +1,2 @@
+- Deprecate install destination paths beginning with ".." to prevent packages
+  escaping their designated installation directories. (#8350, @gridbugs)
diff --git a/src/dune_rules/dune_file.ml b/src/dune_rules/dune_file.ml
index 4b6b9b82cd55..b58946b3cad0 100644
--- a/src/dune_rules/dune_file.ml
+++ b/src/dune_rules/dune_file.ml
@@ -1179,6 +1179,7 @@ module Executables = struct
     type t =
       { names : (Loc.t * string) list
       ; public : public option
+      ; dune_syntax : Syntax.Version.t
       }
 
     let names t = t.names
@@ -1319,7 +1320,7 @@ module Executables = struct
                 (pluralize "public_name" ~multi)
             ]
       in
-      { names; public }
+      { names; public; dune_syntax }
     ;;
 
     let install_conf t ~ext ~enabled_if =
@@ -1328,7 +1329,10 @@ module Executables = struct
           List.map2 t.names public_names ~f:(fun (locn, name) (locp, pub) ->
             Option.map pub ~f:(fun pub ->
               Install_entry.File.of_file_binding
-                (File_binding.Unexpanded.make ~src:(locn, name ^ ext) ~dst:(locp, pub))))
+                (File_binding.Unexpanded.make
+                   ~src:(locn, name ^ ext)
+                   ~dst:(locp, pub)
+                   ~dune_syntax:t.dune_syntax)))
           |> List.filter_opt
         in
         { Install_conf.section = Section Bin
diff --git a/src/dune_rules/file_binding.ml b/src/dune_rules/file_binding.ml
index e690f54642d5..8e193d1c9e47 100644
--- a/src/dune_rules/file_binding.ml
+++ b/src/dune_rules/file_binding.ml
@@ -4,18 +4,69 @@ open Memo.O
 type ('src, 'dst) t =
   { src : 'src
   ; dst : 'dst option
+      (* The [dune_syntax] field is used for validation which has different
+         behaviour depending on the version of dune syntax in use. *)
+  ; dune_syntax : Syntax.Version.t
   }
 
-let equal f g { src; dst } t = f src t.src && Option.equal g dst t.dst
+let equal f g { src; dst; dune_syntax } t =
+  f src t.src
+  && Option.equal g dst t.dst
+  && Syntax.Version.equal dune_syntax t.dune_syntax
+;;
+
+let relative_path_starts_with_parent relative_path =
+  match String.lsplit2 relative_path ~on:'/' with
+  | None -> Filename.(equal relative_path parent_dir_name)
+  | Some (first, _) -> String.equal first Filename.parent_dir_name
+;;
+
+let validate_dst_for_install_stanza
+  ~relative_dst_path_starts_with_parent_error_when
+  ~loc
+  dst
+  dune_syntax
+  =
+  if relative_path_starts_with_parent dst
+  then (
+    match relative_dst_path_starts_with_parent_error_when with
+    | `Deprecation_warning_from_3_11 ->
+      let open Syntax.Version.Infix in
+      if dune_syntax >= (3, 11)
+      then
+        User_warning.emit
+          ~loc
+          [ Pp.textf
+              "The destination path %s begins with %s which will become an error in a \
+               future version of Dune. Destinations of files in install stanzas \
+               beginning with %s will be disallowed to prevent a package's installed \
+               files from escaping that package's install directories."
+              (String.maybe_quoted dst)
+              (String.maybe_quoted Filename.parent_dir_name)
+              (String.maybe_quoted Filename.parent_dir_name)
+          ]
+    | `Always_error ->
+      User_error.raise
+        ~loc
+        [ Pp.textf
+            "The destination path %s begins with %s which is not allowed. Destinations \
+             in install stanzas may not begin with %s to prevent a package's installed \
+             files from escaping that package's install directories."
+            (String.maybe_quoted dst)
+            (String.maybe_quoted Filename.parent_dir_name)
+            (String.maybe_quoted Filename.parent_dir_name)
+        ])
+;;
 
 module Expanded = struct
   type nonrec t = (Loc.t * Path.Build.t, Loc.t * string) t
 
-  let to_dyn { src; dst } =
+  let to_dyn { src; dst; dune_syntax } =
     let open Dyn in
     record
       [ "src", pair Loc.to_dyn Path.Build.to_dyn src
       ; "dst", option (pair Loc.to_dyn string) dst
+      ; "dune_syntax", Syntax.Version.to_dyn dune_syntax
       ]
   ;;
 
@@ -23,7 +74,7 @@ module Expanded = struct
   let dst t = Option.map ~f:snd t.dst
   let src_loc t = fst t.src
 
-  let dst_basename { src = _, src; dst } =
+  let dst_basename { src = _, src; dst; dune_syntax = _ } =
     match dst with
     | Some (_, dst) -> dst
     | None ->
@@ -32,22 +83,35 @@ module Expanded = struct
   ;;
 
   let dst_path t ~dir = Path.Build.relative dir (dst_basename t)
+
+  let validate_for_install_stanza ~relative_dst_path_starts_with_parent_error_when t =
+    Option.iter t.dst ~f:(fun (loc, dst) ->
+      validate_dst_for_install_stanza
+        ~relative_dst_path_starts_with_parent_error_when
+        ~loc
+        dst
+        t.dune_syntax)
+  ;;
 end
 
 module Unexpanded = struct
   type nonrec t = (String_with_vars.t, String_with_vars.t) t
 
-  let to_dyn { src; dst } =
+  let to_dyn { src; dst; dune_syntax } =
     let open Dyn in
     record
-      [ "src", String_with_vars.to_dyn src; "dst", option String_with_vars.to_dyn dst ]
+      [ "src", String_with_vars.to_dyn src
+      ; "dst", option String_with_vars.to_dyn dst
+      ; "dune_syntax", Syntax.Version.to_dyn dune_syntax
+      ]
   ;;
 
   let equal = equal String_with_vars.equal_no_loc String_with_vars.equal_no_loc
 
-  let make ~src:(locs, src) ~dst:(locd, dst) =
+  let make ~src:(locs, src) ~dst:(locd, dst) ~dune_syntax =
     { src = String_with_vars.make_text locs src
     ; dst = Some (String_with_vars.make_text locd dst)
+    ; dune_syntax
     }
   ;;
 
@@ -55,8 +119,19 @@ module Unexpanded = struct
 
   let destination_relative_to_install_path t ~section ~expand ~expand_partial =
     let+ src = expand_partial t.src
-    and+ dst = Memo.Option.map ~f:expand t.dst in
-    Install.Entry.adjust_dst ~section ~src ~dst
+    and+ dst_loc_opt =
+      Memo.Option.map t.dst ~f:(fun dst ->
+        let loc = String_with_vars.loc dst in
+        let+ dst = expand dst in
+        dst, loc)
+    in
+    Option.iter dst_loc_opt ~f:(fun (dst, loc) ->
+      validate_dst_for_install_stanza
+        ~relative_dst_path_starts_with_parent_error_when:`Deprecation_warning_from_3_11
+        ~loc
+        dst
+        t.dune_syntax);
+    Install.Entry.adjust_dst ~section ~src ~dst:(Option.map dst_loc_opt ~f:fst)
   ;;
 
   let expand t ~dir ~f =
@@ -75,7 +150,7 @@ module Unexpanded = struct
         let+ loc, p = f dst in
         Some (loc, p)
     in
-    { src; dst }
+    { src; dst; dune_syntax = t.dune_syntax }
   ;;
 
   let decode =
@@ -87,34 +162,37 @@ module Unexpanded = struct
         | Atom _ -> true
         | _ -> false
       and+ s = String_with_vars.decode
-      and+ version = Dune_lang.Syntax.get_exn Stanza.syntax in
-      if (not is_atom) && version < (1, 6)
+      and+ dune_syntax = Dune_lang.Syntax.get_exn Stanza.syntax in
+      if (not is_atom) && dune_syntax < (1, 6)
       then (
         let what =
           (if String_with_vars.has_pforms s then "variables" else "quoted strings")
           |> sprintf "Using %s here"
         in
         Dune_lang.Syntax.Error.since (String_with_vars.loc s) Stanza.syntax (1, 6) ~what)
-      else s
+      else s, dune_syntax
     in
     peek_exn
     >>= function
-    | Atom _ | Quoted_string _ | Template _ -> decode >>| fun src -> { src; dst = None }
+    | Atom _ | Quoted_string _ | Template _ ->
+      decode >>| fun (src, dune_syntax) -> { src; dst = None; dune_syntax }
     | List (_, [ _; Atom (_, A "as"); _ ]) ->
       enter
-        (let* src = decode in
+        (let* src, dune_syntax = decode in
          keyword "as"
-         >>> let* dst = decode in
-             return { src; dst = Some dst })
+         >>> let* dst, _ = decode in
+             return { src; dst = Some dst; dune_syntax })
     | sexp ->
       User_error.raise
         ~loc:(Dune_lang.Ast.loc sexp)
         [ Pp.text "Invalid format, <name> or (<name> as <install-as>) expected" ]
   ;;
 
+  let dune_syntax t = t.dune_syntax
+
   module L = struct
     let decode = Dune_lang.Decoder.repeat decode
-    let strings_with_vars { src; dst } = src :: Option.to_list dst
+    let strings_with_vars { src; dst; dune_syntax = _ } = src :: Option.to_list dst
 
     let find_pform fbs =
       List.find_map fbs ~f:(fun fb ->
diff --git a/src/dune_rules/file_binding.mli b/src/dune_rules/file_binding.mli
index 6fb5ae8250a0..c1bfd2c2946d 100644
--- a/src/dune_rules/file_binding.mli
+++ b/src/dune_rules/file_binding.mli
@@ -8,6 +8,12 @@ module Expanded : sig
   val dst : t -> string option
   val src_loc : t -> Loc.t
   val dst_path : t -> dir:Path.Build.t -> Path.Build.t
+
+  val validate_for_install_stanza
+    :  relative_dst_path_starts_with_parent_error_when:
+         [ `Deprecation_warning_from_3_11 | `Always_error ]
+    -> t
+    -> unit
 end
 
 module Unexpanded : sig
@@ -15,8 +21,9 @@ module Unexpanded : sig
 
   val to_dyn : t -> Dyn.t
   val equal : t -> t -> bool
-  val make : src:Loc.t * string -> dst:Loc.t * string -> t
+  val make : src:Loc.t * string -> dst:Loc.t * string -> dune_syntax:Syntax.Version.t -> t
   val decode : t Dune_lang.Decoder.t
+  val dune_syntax : t -> Syntax.Version.t
 
   val expand
     :  t
diff --git a/src/dune_rules/gen_rules.ml b/src/dune_rules/gen_rules.ml
index 0f349bb88eb8..6b51ddd5199b 100644
--- a/src/dune_rules/gen_rules.ml
+++ b/src/dune_rules/gen_rules.ml
@@ -236,6 +236,7 @@ let gen_rules
           install_conf.dirs
           ~expand_str
           ~dir:ctx_dir
+          ~relative_dst_path_starts_with_parent_error_when:`Deprecation_warning_from_3_11
       in
       List.map (files_expanded @ dirs_expanded) ~f:(fun fb ->
         File_binding.Expanded.src fb |> Path.build)
diff --git a/src/dune_rules/install_entry.ml b/src/dune_rules/install_entry.ml
index f894700dad28..5987458a1ac5 100644
--- a/src/dune_rules/install_entry.ml
+++ b/src/dune_rules/install_entry.ml
@@ -42,7 +42,7 @@ module File = struct
       file_binding_decode <|> glob_files_decode
     ;;
 
-    let to_file_bindings_unexpanded t ~expand_str ~dir =
+    let to_file_bindings_unexpanded t ~expand_str ~dir ~dune_syntax =
       match t with
       | File_binding file_binding -> Memo.return [ file_binding ]
       | Glob_files glob_files ->
@@ -51,11 +51,11 @@ module File = struct
         let glob_loc = String_with_vars.loc glob_files.glob in
         List.map paths ~f:(fun path ->
           let src = glob_loc, path in
-          File_binding.Unexpanded.make ~src ~dst:src)
+          File_binding.Unexpanded.make ~src ~dst:src ~dune_syntax)
     ;;
 
-    let to_file_bindings_expanded t ~expand_str ~dir =
-      to_file_bindings_unexpanded t ~expand_str ~dir
+    let to_file_bindings_expanded t ~expand_str ~dir ~dune_syntax =
+      to_file_bindings_unexpanded t ~expand_str ~dir ~dune_syntax
       |> Memo.bind
            ~f:
              (Memo.List.map
@@ -66,40 +66,72 @@ module File = struct
     ;;
   end
 
-  type t = Without_include.t Recursive_include.t
+  type t =
+    { entry : Without_include.t Recursive_include.t
+    ; dune_syntax : Syntax.Version.t
+    }
 
   let decode =
-    Recursive_include.decode
-      ~base_term:Without_include.decode
-      ~include_keyword:"include"
-      ~non_sexp_behaviour:`User_error
-      ~include_allowed_in_versions:(`Since (3, 5))
-  ;;
-
-  let expand_include = Recursive_include.expand_include
-
-  let expand_include_multi ts ~expand_str ~dir =
-    Memo.List.concat_map ts ~f:(expand_include ~expand_str ~dir)
+    let open Dune_lang.Decoder in
+    let+ entry =
+      Recursive_include.decode
+        ~base_term:Without_include.decode
+        ~include_keyword:"include"
+        ~non_sexp_behaviour:`User_error
+        ~include_allowed_in_versions:(`Since (3, 5))
+    and+ dune_syntax = Dune_lang.Syntax.get_exn Stanza.syntax in
+    { entry; dune_syntax }
   ;;
 
   let of_file_binding file_binding =
-    Recursive_include.of_base (Without_include.File_binding file_binding)
+    let entry = Recursive_include.of_base (Without_include.File_binding file_binding) in
+    let dune_syntax = File_binding.Unexpanded.dune_syntax file_binding in
+    { entry; dune_syntax }
   ;;
 
   let to_file_bindings_unexpanded ts ~expand_str ~dir =
-    expand_include_multi ts ~expand_str ~dir
+    let open Memo.O in
+    Memo.List.concat_map ts ~f:(fun { entry; dune_syntax } ->
+      let+ with_include_expanded =
+        Recursive_include.expand_include entry ~expand_str ~dir
+      in
+      List.map with_include_expanded ~f:(fun entry -> entry, dune_syntax))
     |> Memo.bind
          ~f:
-           (Memo.List.concat_map
-              ~f:(Without_include.to_file_bindings_unexpanded ~expand_str ~dir))
+           (Memo.List.concat_map ~f:(fun (entry, dune_syntax) ->
+              Without_include.to_file_bindings_unexpanded
+                ~expand_str
+                ~dir
+                ~dune_syntax
+                entry))
   ;;
 
   let to_file_bindings_expanded ts ~expand_str ~dir =
-    expand_include_multi ts ~expand_str ~dir
-    |> Memo.bind
-         ~f:
-           (Memo.List.concat_map
-              ~f:(Without_include.to_file_bindings_expanded ~expand_str ~dir))
+    let open Memo.O in
+    let+ file_bindings_expanded =
+      Memo.List.concat_map ts ~f:(fun { entry; dune_syntax } ->
+        let+ with_include_expanded =
+          Recursive_include.expand_include entry ~expand_str ~dir
+        in
+        List.map with_include_expanded ~f:(fun entry -> entry, dune_syntax))
+      |> Memo.bind
+           ~f:
+             (Memo.List.concat_map ~f:(fun (entry, dune_syntax) ->
+                Without_include.to_file_bindings_expanded
+                  ~expand_str
+                  ~dir
+                  ~dune_syntax
+                  entry))
+    in
+    (* Note that validation is deferred until after file bindings have been
+       expanded as a path may be invalid due to the contents of a variable
+       whose value is unknown until prior to this point. *)
+    List.iter
+      file_bindings_expanded
+      ~f:
+        (File_binding.Expanded.validate_for_install_stanza
+           ~relative_dst_path_starts_with_parent_error_when:`Deprecation_warning_from_3_11);
+    file_bindings_expanded
   ;;
 end
 
@@ -114,14 +146,29 @@ module Dir = struct
 
   type t = File_binding.Unexpanded.t Recursive_include.t
 
-  let to_file_bindings_expanded ts ~expand_str ~dir =
-    Memo.List.concat_map ts ~f:(Recursive_include.expand_include ~expand_str ~dir)
-    |> Memo.bind
-         ~f:
-           (Memo.List.map
-              ~f:
-                (File_binding.Unexpanded.expand
-                   ~dir
-                   ~f:(expand_str_with_check_for_local_path ~expand_str)))
+  let to_file_bindings_expanded
+    ts
+    ~expand_str
+    ~dir
+    ~relative_dst_path_starts_with_parent_error_when
+    =
+    let open Memo.O in
+    let+ file_bindings_expanded =
+      Memo.List.concat_map ts ~f:(Recursive_include.expand_include ~expand_str ~dir)
+      >>= Memo.List.map
+            ~f:
+              (File_binding.Unexpanded.expand
+                 ~dir
+                 ~f:(expand_str_with_check_for_local_path ~expand_str))
+    in
+    (* Note that validation is deferred until after file bindings have been
+       expanded as a path may be invalid due to the contents of a variable
+       whose value is unknown until prior to this point. *)
+    List.iter
+      file_bindings_expanded
+      ~f:
+        (File_binding.Expanded.validate_for_install_stanza
+           ~relative_dst_path_starts_with_parent_error_when);
+    file_bindings_expanded
   ;;
 end
diff --git a/src/dune_rules/install_entry.mli b/src/dune_rules/install_entry.mli
index d046e190c681..e395885a134f 100644
--- a/src/dune_rules/install_entry.mli
+++ b/src/dune_rules/install_entry.mli
@@ -36,5 +36,7 @@ module Dir : sig
     :  t list
     -> expand_str:(String_with_vars.t -> string Memo.t)
     -> dir:Path.Build.t
+    -> relative_dst_path_starts_with_parent_error_when:
+         [ `Deprecation_warning_from_3_11 | `Always_error ]
     -> File_binding.Expanded.t list Memo.t
 end
diff --git a/src/dune_rules/install_rules.ml b/src/dune_rules/install_rules.ml
index 4d5d06283604..48627bb74f33 100644
--- a/src/dune_rules/install_rules.ml
+++ b/src/dune_rules/install_rules.ml
@@ -391,14 +391,26 @@ end = struct
         Install.Entry.Sourced.create ~loc entry)
     and+ files_from_dirs =
       let* dirs_expanded =
-        Install_entry.Dir.to_file_bindings_expanded i.dirs ~expand_str ~dir
+        Install_entry.Dir.to_file_bindings_expanded
+          i.dirs
+          ~expand_str
+          ~dir
+          ~relative_dst_path_starts_with_parent_error_when:`Deprecation_warning_from_3_11
       in
       Memo.List.map dirs_expanded ~f:(fun fb ->
         let loc = File_binding.Expanded.src_loc fb in
         let+ entry = make_entry ~kind:`Directory fb in
         Install.Entry.Sourced.create ~loc entry)
     and+ source_trees =
-      Install_entry.Dir.to_file_bindings_expanded i.source_trees ~expand_str ~dir
+      (* There's no deprecation warning when a relative destination path
+         starts with a parent in this feature. It's safe to raise an error in
+         this case as installing source trees was added in the same dune version
+         that we deprecated starting a destination install path with "..". *)
+      Install_entry.Dir.to_file_bindings_expanded
+        i.source_trees
+        ~expand_str
+        ~dir
+        ~relative_dst_path_starts_with_parent_error_when:`Always_error
       >>= Memo.List.map ~f:(fun fb ->
         let loc = File_binding.Expanded.src_loc fb in
         let* entry = make_entry ~kind:`Source_tree fb in
diff --git a/test/blackbox-tests/test-cases/install/install-glob/install-glob-relative.t b/test/blackbox-tests/test-cases/install/install-glob/install-glob-relative.t
index f01522f0f1c4..607d964a0a4b 100644
--- a/test/blackbox-tests/test-cases/install/install-glob/install-glob-relative.t
+++ b/test/blackbox-tests/test-cases/install/install-glob/install-glob-relative.t
@@ -1,10 +1,11 @@
 Install a glob pattern that uses a relative path.
 
-When we use a pattern such as ../foo/*, the relative path leaks into the
-installation destination and can escape the root of the installed package.
+Test that dune detects an error when we use a pattern such as ../foo/* in the
+install stanza. The problem with this pattern is its destination refers to a
+path outside the package's install directory.
 
   $ cat >dune-project <<EOF
-  > (lang dune 3.6)
+  > (lang dune 3.11)
   > (package (name foo))
   > EOF
 
@@ -19,8 +20,7 @@ normal install stanza in the share directory of the package:
   >  (files stuff/foo.txt))
   > EOF
 
-faulty stanza that install things outside the package:
-
+Incorrect install stanza that would place files outside the package's install directory
   $ cat >stanza/dune <<EOF
   > (install
   >  (files (glob_files_rec ../stuff/*.txt))
@@ -28,17 +28,18 @@ faulty stanza that install things outside the package:
   > EOF
 
   $ dune build foo.install
+  File "stanza/dune", line 2, characters 24-38:
+  2 |  (files (glob_files_rec ../stuff/*.txt))
+                              ^^^^^^^^^^^^^^
+  Warning: The destination path ../stuff/foo.txt begins with .. which will
+  become an error in a future version of Dune. Destinations of files in install
+  stanzas beginning with .. will be disallowed to prevent a package's installed
+  files from escaping that package's install directories.
+  File "stanza/dune", line 2, characters 24-38:
+  2 |  (files (glob_files_rec ../stuff/*.txt))
+                              ^^^^^^^^^^^^^^
+  Warning: The destination path ../stuff/xy/bar.txt begins with .. which will
+  become an error in a future version of Dune. Destinations of files in install
+  stanzas beginning with .. will be disallowed to prevent a package's installed
+  files from escaping that package's install directories.
 
-Note that the "stuff" paths from  are now going to be installed outside the
-package.
-
-  $ grep txt _build/default/foo.install
-    "_build/install/default/share/stuff/foo.txt" {"../stuff/foo.txt"}
-    "_build/install/default/share/stuff/xy/bar.txt" {"../stuff/xy/bar.txt"}
-    "_build/install/default/share/foo/foo.txt"
-
-  $ dune install foo --prefix _foo
-  $ find _foo | sort | grep txt
-  _foo/share/foo/foo.txt
-  _foo/share/stuff/foo.txt
-  _foo/share/stuff/xy/bar.txt
diff --git a/test/blackbox-tests/test-cases/install/install-source-tree.t b/test/blackbox-tests/test-cases/install/install-source-tree.t
index 392c8f80eba1..2fd2e12e4260 100644
--- a/test/blackbox-tests/test-cases/install/install-source-tree.t
+++ b/test/blackbox-tests/test-cases/install/install-source-tree.t
@@ -63,13 +63,12 @@ Create the source directory and fill it up with some dummy stuff for the test:
     "_build/install/default/doc/mypkg/your/docs/foo/bar.md" {"your/docs/foo/bar.md"}
   ]
 
+It is an error for the destination path to start with "..".
   $ test "(mydocs as ../)"
-  lib: [
-    "_build/install/default/lib/mypkg/META"
-    "_build/install/default/lib/mypkg/dune-package"
-  ]
-  doc: [
-    "_build/install/default/doc/baz.md" {"../baz.md"}
-    "_build/install/default/doc/foo.md" {"../foo.md"}
-    "_build/install/default/doc/foo/bar.md" {"../foo/bar.md"}
-  ]
+  File "dune", line 3, characters 26-29:
+  3 |  (source_trees (mydocs as ../)))
+                                ^^^
+  Error: The destination path ../ begins with .. which is not allowed.
+  Destinations in install stanzas may not begin with .. to prevent a package's
+  installed files from escaping that package's install directories.
+  [1]
diff --git a/test/blackbox-tests/test-cases/start-install-dst-with-parent-error.t b/test/blackbox-tests/test-cases/start-install-dst-with-parent-error.t
new file mode 100644
index 000000000000..82c368aa9cef
--- /dev/null
+++ b/test/blackbox-tests/test-cases/start-install-dst-with-parent-error.t
@@ -0,0 +1,181 @@
+Test for the case where the destination of an install stanza entry would place a
+file outside of the directories associated with the package. This behaviour was
+deprecated in 3.11.
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.11)
+  > (package
+  >  (name foo))
+  > (using directory-targets 0.1)
+  > EOF
+
+Create a file to install
+  $ mkdir a
+  $ touch a/b.txt
+
+Test that we get a warning if `(files ...)` has a dst starting with "..":
+  $ cat >dune <<EOF
+  > (install
+  >  (section etc)
+  >  (files (a/b.txt as ../b)))
+  > EOF
+  $ dune build foo.install && cat _build/default/foo.install
+  File "dune", line 3, characters 20-24:
+  3 |  (files (a/b.txt as ../b)))
+                          ^^^^
+  Warning: The destination path ../b begins with .. which will become an error
+  in a future version of Dune. Destinations of files in install stanzas
+  beginning with .. will be disallowed to prevent a package's installed files
+  from escaping that package's install directories.
+  lib: [
+    "_build/install/default/lib/foo/META"
+    "_build/install/default/lib/foo/dune-package"
+  ]
+  etc: [
+    "_build/install/default/etc/b" {"../b"}
+  ]
+
+Test that we get a warning if `(dirs ...)` has a dst starting with "..":
+  $ cat >dune <<EOF
+  > (rule
+  >  (target (dir bar))
+  >  (action (progn (run mkdir bar) (run touch bar/baz.txt))))
+  > 
+  > (install
+  >  (section etc)
+  >  (dirs (bar as ../baz)))
+  > EOF
+  $ dune build foo.install && cat _build/default/foo.install
+  File "dune", line 7, characters 15-21:
+  7 |  (dirs (bar as ../baz)))
+                     ^^^^^^
+  Warning: The destination path ../baz begins with .. which will become an
+  error in a future version of Dune. Destinations of files in install stanzas
+  beginning with .. will be disallowed to prevent a package's installed files
+  from escaping that package's install directories.
+  lib: [
+    "_build/install/default/lib/foo/META"
+    "_build/install/default/lib/foo/dune-package"
+  ]
+  etc: [
+    "_build/install/default/etc/baz/baz.txt" {"../baz/baz.txt"}
+  ]
+
+Test that we get a warning if `(dirs ...)` has a dst that is exactly "..":
+  $ cat >dune <<EOF
+  > (rule
+  >  (target (dir bar))
+  >  (action (progn (run mkdir bar) (run touch bar/baz.txt))))
+  > 
+  > (install
+  >  (section etc)
+  >  (dirs (bar as ..)))
+  > EOF
+  $ dune build foo.install && cat _build/default/foo.install
+  File "dune", line 7, characters 15-17:
+  7 |  (dirs (bar as ..)))
+                     ^^
+  Warning: The destination path .. begins with .. which will become an error in
+  a future version of Dune. Destinations of files in install stanzas beginning
+  with .. will be disallowed to prevent a package's installed files from
+  escaping that package's install directories.
+  lib: [
+    "_build/install/default/lib/foo/META"
+    "_build/install/default/lib/foo/dune-package"
+  ]
+  etc: [
+    "_build/install/default/etc/baz.txt" {"../baz.txt"}
+  ]
+
+Test that we get get a warning if the ".." is the result of variable expansion:
+  $ printf ".." > prefix.txt
+  $ cat >dune <<EOF
+  > (install
+  >  (section etc)
+  >  (files (a/b.txt as %{read:prefix.txt}/b)))
+  > EOF
+  $ dune build foo.install && cat _build/default/foo.install
+  File "dune", line 3, characters 20-40:
+  3 |  (files (a/b.txt as %{read:prefix.txt}/b)))
+                          ^^^^^^^^^^^^^^^^^^^^
+  Warning: The destination path ../b begins with .. which will become an error
+  in a future version of Dune. Destinations of files in install stanzas
+  beginning with .. will be disallowed to prevent a package's installed files
+  from escaping that package's install directories.
+  lib: [
+    "_build/install/default/lib/foo/META"
+    "_build/install/default/lib/foo/dune-package"
+  ]
+  etc: [
+    "_build/install/default/etc/b" {"../b"}
+  ]
+
+Test that we get an error if `(source_tree ...)` has a dst starting with "..".
+This is an error rather than a warning as installing source trees is added in
+the same version of dune as starting a dest with ".." was deprecated.
+  $ cat >dune <<EOF
+  > (install
+  >  (section etc)
+  >  (source_trees (a as ../b)))
+  > EOF
+  $ dune build foo.install
+  File "dune", line 3, characters 21-25:
+  3 |  (source_trees (a as ../b)))
+                           ^^^^
+  Error: The destination path ../b begins with .. which is not allowed.
+  Destinations in install stanzas may not begin with .. to prevent a package's
+  installed files from escaping that package's install directories.
+  [1]
+
+Test that we get an error if `(source_tree ...)` has a dst that is exactly "..":
+  $ cat >dune <<EOF
+  > (install
+  >  (section etc)
+  >  (source_trees (a as ..)))
+  > EOF
+  $ dune build foo.install
+  File "dune", line 3, characters 21-23:
+  3 |  (source_trees (a as ..)))
+                           ^^
+  Error: The destination path .. begins with .. which is not allowed.
+  Destinations in install stanzas may not begin with .. to prevent a package's
+  installed files from escaping that package's install directories.
+  [1]
+
+Test that on older versions of dune we don't get warnings in this case:
+  $ cat >dune-project <<EOF
+  > (lang dune 3.10)
+  > (package
+  >  (name foo))
+  > (using directory-targets 0.1)
+  > EOF
+
+  $ cat >dune <<EOF
+  > (install
+  >  (section etc)
+  >  (files (a/b.txt as ../b)))
+  > 
+  > (rule
+  >  (target (dir bar))
+  >  (action (progn (run mkdir bar) (run touch bar/baz.txt))))
+  > 
+  > (install
+  >  (section etc)
+  >  (dirs (bar as ../baz)))
+  > 
+  > (install
+  >  (section share)
+  >  (dirs (bar as ..)))
+  > EOF
+  $ dune build foo.install && cat _build/default/foo.install
+  lib: [
+    "_build/install/default/lib/foo/META"
+    "_build/install/default/lib/foo/dune-package"
+  ]
+  share: [
+    "_build/install/default/share/baz.txt" {"../baz.txt"}
+  ]
+  etc: [
+    "_build/install/default/etc/b" {"../b"}
+    "_build/install/default/etc/baz/baz.txt" {"../baz/baz.txt"}
+  ]