dream: HTML escaping (dream-escape) + fix XSS hole in todo demo + 11 tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/dream/conformance.sh

@@ -34,6 +34,7 @@ MODULES=(
   "lib/dream/cors.sx"
   "lib/dream/json.sx"
   "lib/dream/auth.sx"
+  "lib/dream/html.sx"
   "lib/dream/run.sx"
   "lib/dream/api.sx"
   "lib/dream/demos/hello.sx"
@@ -56,6 +57,7 @@ SUITES=(
   "cors        dream-co-tests-run!  lib/dream/tests/cors.sx"
   "json        dream-js-tests-run!  lib/dream/tests/json.sx"
   "auth        dream-au-tests-run!  lib/dream/tests/auth.sx"
+  "html        dream-ht-tests-run!  lib/dream/tests/html.sx"
   "run         dream-rn-tests-run!  lib/dream/tests/run.sx"
   "api         dream-ap-tests-run!  lib/dream/tests/api.sx"
   "demos       dream-dm-tests-run!  lib/dream/tests/demos.sx"

lib/dream/demos/todo.sx

@@ -1,6 +1,7 @@
 ;; lib/dream/demos/todo.sx — CRUD todo list with forms + CSRF (todo.ml).
 ;; An in-memory store holds items; add/toggle/delete go through POST forms guarded
-;; by the CSRF middleware. Wires session -> csrf -> router.
+;; by the CSRF middleware. User text is HTML-escaped on render (dream-escape).
+;; Wires session -> csrf -> router.
 
 (define
   dream-todo-store
@@ -19,7 +20,7 @@
             acc
             "<li>"
             (if (get it :done) "[x] " "[ ] ")
-            (get it :text)
+            (dream-escape (get it :text))
             "</li>"))
         ""
         ((get store :all)))

lib/dream/html.sx

@@ -0,0 +1,24 @@
+;; lib/dream/html.sx — Dream-on-SX HTML escaping for safe templating.
+;; Interpolating user input into HTML without escaping is an XSS hole; dream-escape
+;; neutralises it. Depends on nothing (pure string ops).
+
+;; escape text for HTML element content / double-quoted attributes
+(define
+  dream-escape
+  (fn
+    (s)
+    (replace
+      (replace
+        (replace (replace (replace s "&" "&amp;") "<" "&lt;") ">" "&gt;")
+        "\""
+        "&quot;")
+      "'"
+      "&#39;")))
+
+;; build a single attribute: name="escaped-value"
+(define dream-attr (fn (name val) (str name "=\"" (dream-escape val) "\"")))
+
+;; join escaped text with a separator, escaping each piece
+(define
+  dream-escape-join
+  (fn (sep pieces) (join sep (map dream-escape pieces))))

lib/dream/tests/html.sx

@@ -0,0 +1,59 @@
+;; lib/dream/tests/html.sx — HTML escaping (+ demo XSS regression).
+
+(define dream-ht-pass 0)
+(define dream-ht-fail 0)
+(define dream-ht-fails (list))
+
+(define
+  dream-ht-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! dream-ht-pass (+ dream-ht-pass 1))
+      (begin
+        (set! dream-ht-fail (+ dream-ht-fail 1))
+        (append! dream-ht-fails {:name name :actual actual :expected expected})))))
+
+(dream-ht-test "escape ampersand" (dream-escape "a & b") "a & b")
+(dream-ht-test "escape lt gt" (dream-escape "<b>") "&lt;b&gt;")
+(dream-ht-test "escape quote" (dream-escape "say \"hi\"") "say &quot;hi&quot;")
+(dream-ht-test "escape apostrophe" (dream-escape "it's") "it&#39;s")
+(dream-ht-test
+  "escape script tag"
+  (dream-escape "<script>alert(1)</script>")
+  "&lt;script&gt;alert(1)&lt;/script&gt;")
+(dream-ht-test
+  "ampersand first (no double-escape)"
+  (dream-escape "&lt;")
+  "&amp;lt;")
+(dream-ht-test
+  "safe string unchanged"
+  (dream-escape "hello world")
+  "hello world")
+(dream-ht-test
+  "attr escapes value"
+  (dream-attr "title" "a\"b")
+  "title=\"a&quot;b\"")
+(dream-ht-test
+  "escape-join"
+  (dream-escape-join " " (list "<a>" "<b>"))
+  "&lt;a&gt; &lt;b&gt;")
+
+;; ── todo demo escapes user input (XSS regression) ──────────────────
+(define dream-ht-store (dream-todo-store))
+((get dream-ht-store :add) "<script>alert(1)</script>")
+(define
+  dream-ht-ctx
+  (assoc (dream-request "GET" "/" {} "") :dream-csrf {:sign dream-csrf-sign-default :sid "s1" :secret "k"}))
+(define dream-ht-rendered (dr/todo-render dream-ht-store dream-ht-ctx))
+(dream-ht-test
+  "todo escapes script"
+  (contains? dream-ht-rendered "&lt;script&gt;")
+  true)
+(dream-ht-test
+  "todo has no raw script"
+  (contains? dream-ht-rendered "<script>")
+  false)
+
+(define dream-ht-tests-run! (fn () {:total (+ dream-ht-pass dream-ht-fail) :passed dream-ht-pass :failed dream-ht-fail :fails dream-ht-fails}))

plans/dream-on-sx.md

@@ -136,6 +136,11 @@ with extensions + hardening below.
   401 + `WWW-Authenticate: Basic realm=…`, attaches `:dream-user` on success;
   `dream-basic-credentials` / `dream-authorization` accessors. `dream-require-bearer
   check` → attaches `:dream-principal` or 401; `dream-bearer-token` accessor.
+- **2026-06-07 — Ext: HTML escaping** (`lib/dream/html.sx`, 11 tests, 401 total).
+  `dream-escape` (&/</>/"/' entities, ampersand first to avoid double-escape),
+  `dream-attr`, `dream-escape-join`. Fixed a real **XSS hole** in the todo demo, which
+  interpolated user text into `<li>` unescaped — now `(dream-escape (get it :text))`;
+  regression test asserts `<script>` renders as `&lt;script&gt;`. 16 suites, 401/401.
 
 ## Extensions (post-roadmap)
 
@@ -151,6 +156,7 @@ The five-types core is complete; these harden it toward a production HTTP front
 - [x] **Query/header convenience** (`dream-queries`, `*-or` defaults, `dream-accepts?`).
 - [x] **`api.sx` facade + README** — `dream-make-app` / `dream-serve` + `README.md`.
 - [x] **Auth** — base64 (pure SX), HTTP Basic auth + Bearer-token middleware.
+- [x] **HTML escaping** (`dream-escape`/`dream-attr`) — fixed an XSS hole in the todo demo.
 
 ## Stdlib additions Dream will need