fix(security): escape user input in HTML gallery to prevent stored XSS (#16958)

* Security/openai-image-gen: escape HTML gallery user input

* Tests/openai-image-gen: add gallery XSS regression coverage

* Changelog: add openai-image-gen XSS hardening note

---------

Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

skills/openai-image-gen/scripts/gen.py

@@ -9,6 +9,7 @@ import re
 import sys
 import urllib.error
 import urllib.request
+from html import escape as html_escape
 from pathlib import Path
 
 
@@ -131,8 +132,8 @@ def write_gallery(out_dir: Path, items: list[dict]) -> None:
         [
             f"""
 <figure>
-  <a href="{it["file"]}"><img src="{it["file"]}" loading="lazy" /></a>
-  <figcaption>{it["prompt"]}</figcaption>
+  <a href="{html_escape(it["file"], quote=True)}"><img src="{html_escape(it["file"], quote=True)}" loading="lazy" /></a>
+  <figcaption>{html_escape(it["prompt"])}</figcaption>
 </figure>
 """.strip()
             for it in items
@@ -152,7 +153,7 @@ def write_gallery(out_dir: Path, items: list[dict]) -> None:
   code {{ color: #9cd1ff; }}
 </style>
 <h1>openai-image-gen</h1>
-<p>Output: <code>{out_dir.as_posix()}</code></p>
+<p>Output: <code>{html_escape(out_dir.as_posix())}</code></p>
 <div class="grid">
 {thumbs}
 </div>

skills/openai-image-gen/scripts/test_gen.py

@@ -0,0 +1,50 @@
+"""Tests for write_gallery HTML escaping (fixes #12538 - stored XSS)."""
+
+import tempfile
+from pathlib import Path
+
+from gen import write_gallery
+
+
+def test_write_gallery_escapes_prompt_xss():
+    with tempfile.TemporaryDirectory() as tmpdir:
+        out = Path(tmpdir)
+        items = [{"prompt": '<script>alert("xss")</script>', "file": "001-test.png"}]
+        write_gallery(out, items)
+        html = (out / "index.html").read_text()
+        assert "<script>" not in html
+        assert "&lt;script&gt;" in html
+
+
+def test_write_gallery_escapes_filename():
+    with tempfile.TemporaryDirectory() as tmpdir:
+        out = Path(tmpdir)
+        items = [{"prompt": "safe prompt", "file": '" onload="alert(1)'}]
+        write_gallery(out, items)
+        html = (out / "index.html").read_text()
+        assert 'onload="alert(1)"' not in html
+        assert "&quot;" in html
+
+
+def test_write_gallery_escapes_ampersand():
+    with tempfile.TemporaryDirectory() as tmpdir:
+        out = Path(tmpdir)
+        items = [{"prompt": "cats & dogs <3", "file": "001-test.png"}]
+        write_gallery(out, items)
+        html = (out / "index.html").read_text()
+        assert "cats &amp; dogs &lt;3" in html
+
+
+def test_write_gallery_normal_output():
+    with tempfile.TemporaryDirectory() as tmpdir:
+        out = Path(tmpdir)
+        items = [
+            {"prompt": "a lobster astronaut, golden hour", "file": "001-lobster.png"},
+            {"prompt": "a cozy reading nook", "file": "002-nook.png"},
+        ]
+        write_gallery(out, items)
+        html = (out / "index.html").read_text()
+        assert "a lobster astronaut, golden hour" in html
+        assert 'src="001-lobster.png"' in html
+        assert "002-nook.png" in html
+