From 8027fc5a06e917a93d2c6c877488f14082b3fbba Mon Sep 17 00:00:00 2001
From: "L. David Baron" <dbaron@dbaron.org>
Date: Tue, 19 Dec 2023 22:02:15 -0500
Subject: [PATCH] Forbid nesting <details> in the same exclusive accordion

Fixes #9968.
---
 source | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/source b/source
index 719a9e00795..dffcc9efcd2 100644
--- a/source
+++ b/source
@@ -60194,6 +60194,9 @@ interface <dfn interface>HTMLDetailsElement</dfn> : <span>HTMLElement</span> {
   data-x="attr-details-open">open</code> attributes in the markup.  This requirement on authors
   forbids such misleading markup.</p>
 
+  <p>A document must not contain a <code>details</code> element that is a descendant of another
+  <code>details</code> element in the same <span>details name group</span>.</p>
+
   <p>Documents that use the <code data-x="attr-details-name">name</code> attribute to group multiple
   related <code>details</code> elements should keep those related elements together in a containing
   element (such as a <code>section</code> element).</p>