diff --git a/LayoutTests/imported/w3c/web-platform-tests/trusted-types/block-Document-execCommand-expected.txt b/LayoutTests/imported/w3c/web-platform-tests/trusted-types/block-Document-execCommand-expected.txt
index 52242ff5f0a2..56069ed1a1dd 100644
--- a/LayoutTests/imported/w3c/web-platform-tests/trusted-types/block-Document-execCommand-expected.txt
+++ b/LayoutTests/imported/w3c/web-platform-tests/trusted-types/block-Document-execCommand-expected.txt
@@ -1,5 +1,6 @@
+CONSOLE MESSAGE: This requires a TrustedHTML value else it violates the following Content Security Policy directive: "require-trusted-types-for 'script'"
 
-FAIL Document.execCommand("insertHTML") throws. assert_throws_js: function "_ => document.execCommand(command, false, "<em>Hello World</em>")" did not throw
+PASS Document.execCommand("insertHTML") throws.
 PASS Document.execCommand("insertHTML") works with a TrustedHTML argument.
 PASS Document.execCommand("paste") works as usual."
 PASS Document.execCommand("paste") works with a TrustedHTML argument.
diff --git a/Source/WebCore/dom/Document+HTML.idl b/Source/WebCore/dom/Document+HTML.idl
index d9fe8ab2add8..602ceb7309f6 100644
--- a/Source/WebCore/dom/Document+HTML.idl
+++ b/Source/WebCore/dom/Document+HTML.idl
@@ -68,7 +68,7 @@ partial interface Document {
     [ImplementedAs=windowProxy] readonly attribute WindowProxy? defaultView;
     boolean hasFocus();
     [CEReactions=Needed] attribute DOMString designMode;
-    [CEReactions=Needed] boolean execCommand(DOMString commandId, optional boolean showUI = false, optional DOMString value = "");
+    [CEReactions=Needed] boolean execCommand(DOMString commandId, optional boolean showUI = false, optional (DOMString or TrustedHTML) value = "");
     boolean queryCommandEnabled(DOMString commandId);
     boolean queryCommandIndeterm(DOMString commandId);
     boolean queryCommandState(DOMString commandId);
diff --git a/Source/WebCore/dom/Document.cpp b/Source/WebCore/dom/Document.cpp
index e3fc31129fd3..6e3f29790c6c 100644
--- a/Source/WebCore/dom/Document.cpp
+++ b/Source/WebCore/dom/Document.cpp
@@ -272,6 +272,7 @@
 #include "TouchAction.h"
 #include "TransformSource.h"
 #include "TreeWalker.h"
+#include "TrustedType.h"
 #include "TypedElementDescendantIteratorInlines.h"
 #include "UndoManager.h"
 #include "UserGestureIndicator.h"
@@ -6895,13 +6896,27 @@ static Editor::Command command(Document* document, const String& commandName, bo
         userInterface ? EditorCommandSource::DOMWithUserInterface : EditorCommandSource::DOM);
 }
 
-ExceptionOr<bool> Document::execCommand(const String& commandName, bool userInterface, const String& value)
+ExceptionOr<bool> Document::execCommand(const String& commandName, bool userInterface, const std::variant<String, RefPtr<TrustedHTML>>& value)
 {
     if (UNLIKELY(!isHTMLDocument() && !isXHTMLDocument()))
         return Exception { ExceptionCode::InvalidStateError, "execCommand is only supported on HTML documents."_s };
 
+    auto stringValueHolder = WTF::switchOn(value,
+        [&commandName, this](const String& str) -> ExceptionOr<String> {
+            if (commandName != "insertHTML"_s)
+                return String(str);
+            return trustedTypeCompliantString(TrustedType::TrustedHTML, *scriptExecutionContext(), str, "Document execCommand"_s);
+        },
+        [](const RefPtr<TrustedHTML>& trustedHtml) -> ExceptionOr<String> {
+            return trustedHtml->toString();
+        }
+    );
+
+    if (stringValueHolder.hasException())
+        return stringValueHolder.releaseException();
+
     EventQueueScope eventQueueScope;
-    return command(this, commandName, userInterface).execute(value);
+    return command(this, commandName, userInterface).execute(stringValueHolder.releaseReturnValue());
 }
 
 ExceptionOr<bool> Document::queryCommandEnabled(const String& commandName)
diff --git a/Source/WebCore/dom/Document.h b/Source/WebCore/dom/Document.h
index 9476aaf98f81..e33017edd227 100644
--- a/Source/WebCore/dom/Document.h
+++ b/Source/WebCore/dom/Document.h
@@ -46,6 +46,7 @@
 #include "Supplementable.h"
 #include "Timer.h"
 #include "TreeScope.h"
+#include "TrustedHTML.h"
 #include "URLKeepingBlobAlive.h"
 #include "UserActionElementSet.h"
 #include "ViewportArguments.h"
@@ -1197,7 +1198,7 @@ class Document
     inline CheckedRef<DocumentMarkerController> checkedMarkers(); // Defined in DocumentInlines.h.
     inline CheckedRef<const DocumentMarkerController> checkedMarkers() const; // Defined in DocumentInlines.h.
 
-    WEBCORE_EXPORT ExceptionOr<bool> execCommand(const String& command, bool userInterface = false, const String& value = String());
+    WEBCORE_EXPORT ExceptionOr<bool> execCommand(const String& command, bool userInterface = false, const std::variant<String, RefPtr<TrustedHTML>>& value = String());
     WEBCORE_EXPORT ExceptionOr<bool> queryCommandEnabled(const String& command);
     WEBCORE_EXPORT ExceptionOr<bool> queryCommandIndeterm(const String& command);
     WEBCORE_EXPORT ExceptionOr<bool> queryCommandState(const String& command);
diff --git a/Source/WebCore/dom/TrustedHTML.h b/Source/WebCore/dom/TrustedHTML.h
index 76a6b777b3c0..8dfdcdedfeb6 100644
--- a/Source/WebCore/dom/TrustedHTML.h
+++ b/Source/WebCore/dom/TrustedHTML.h
@@ -31,7 +31,7 @@
 
 namespace WebCore {
 
-class TrustedHTML : public ScriptWrappable, public RefCounted<TrustedHTML> {
+class WEBCORE_EXPORT TrustedHTML : public ScriptWrappable, public RefCounted<TrustedHTML> {
     WTF_MAKE_ISO_ALLOCATED(TrustedHTML);
 public:
     static Ref<TrustedHTML> create(const String& data);