diff --git a/addons/wiki/models.py b/addons/wiki/models.py
index e20f40dd730..f8c6a1bf75f 100644
--- a/addons/wiki/models.py
+++ b/addons/wiki/models.py
@@ -266,7 +266,16 @@ def get_for_node(self, node, name=None, id=None):
                 deleted__isnull=True,
                 node=node,
             ).order_by('created', 'id').first()
-        return WikiPage.load(id)
+        if id:
+            wiki_page = WikiPage.load(id)
+            # Restrict by node so wid cannot leak another project's page name.
+            if (
+                wiki_page
+                and wiki_page.deleted is None
+                and wiki_page.node_id == node.id
+            ):
+                return wiki_page
+        return None
 
     def get_for_child_nodes(self, node, parent=None):
         if parent:
diff --git a/addons/wiki/tests/test_wiki.py b/addons/wiki/tests/test_wiki.py
index d6f267a6fb5..3be7918e3e3 100644
--- a/addons/wiki/tests/test_wiki.py
+++ b/addons/wiki/tests/test_wiki.py
@@ -448,6 +448,17 @@ def test_wiki_id_url_get_returns_404(self):
         res = self.app.get(url, expect_errors=True)
         assert_equal(res.status_code, 404)
 
+    def test_wiki_id_url_get_returns_404_for_other_node_wiki(self):
+        other = ProjectFactory(is_public=True, creator=self.user)
+        other_page = WikiPage.objects.create_for_node(
+            other, 'SecretFromOther', 'content', Auth(self.user)
+        )
+        url = self.project.web_url_for(
+            'project_wiki_id_page', wid=other_page._primary_key, _guid=True
+        )
+        res = self.app.get(url, expect_errors=True)
+        assert_equal(res.status_code, 404)
+
     def test_home_is_capitalized_in_web_view(self):
         url = self.project.web_url_for('project_wiki_home', wid='home', _guid=True)
         res = self.app.get(url, auth=self.user.auth).follow(auth=self.user.auth)
@@ -3390,6 +3401,24 @@ def test_bulk_update_wiki_sort(self):
         self.assertEqual(result_wiki_child_page2, {'parent_id': wiki_page2_id, 'sort_order': 1})
         self.assertEqual(result_wiki_child_page3, {'parent_id': wiki_child_page2_id, 'sort_order': 1})
 
+    def test_bulk_update_wiki_sort_rejects_cross_node_parent(self):
+        other = ProjectFactory(is_public=True, creator=self.user)
+        other_page = WikiPage.objects.create_for_node(
+            other, 'other project wiki', 'content', self.consolidate_auth
+        )
+        other_guid = other_page.guids.first()._id
+        parent_before = self.wiki_page1.parent_id
+        sort_id_list = [self.guid1]
+        sort_num_list = [1]
+        parent_wiki_id_list = [other_guid]
+        with self.assertRaises(HTTPError) as cm:
+            views._bulk_update_wiki_sort(
+                self.project, sort_id_list, sort_num_list, parent_wiki_id_list
+            )
+        self.assertEqual(cm.exception.code, http_status.HTTP_400_BAD_REQUEST)
+        self.wiki_page1.reload()
+        self.assertEqual(self.wiki_page1.parent_id, parent_before)
+
     def _wiki_sort_payload(self):
         return {
             'sortedData': [
@@ -3431,6 +3460,39 @@ def test_project_update_wiki_page_sort(self):
         self.assertEqual(result_wiki_child_page2, {'parent_id': wiki_page2_id, 'sort_order': 2})
         self.assertEqual(result_wiki_child_page3, {'parent_id': wiki_child_page2_id, 'sort_order': 1})
 
+    def test_project_update_wiki_page_sort_rejects_cross_node_parent(self):
+        other = ProjectFactory(is_public=True, creator=self.user)
+        other_page = WikiPage.objects.create_for_node(
+            other, 'other project wiki', 'content', self.consolidate_auth
+        )
+        other_guid = other_page.guids.first()._id
+        parent_before = self.wiki_page1.parent_id
+        url = self.project.api_url_for('project_update_wiki_page_sort')
+        # Nest a local wiki under another project's wiki id as parent.
+        payload = {
+            'sortedData': [
+                {
+                    'name': 'other as parent',
+                    'id': other_guid,
+                    'sortOrder': 1,
+                    'children': [
+                        {
+                            'name': 'wiki page1',
+                            'id': self.guid1,
+                            'sortOrder': 1,
+                            'children': [],
+                            'fold': False,
+                        }
+                    ],
+                    'fold': False,
+                }
+            ]
+        }
+        res = self.app.post_json(url, payload, auth=self.user.auth, expect_errors=True)
+        assert_equal(res.status_code, http_status.HTTP_400_BAD_REQUEST)
+        self.wiki_page1.reload()
+        self.assertEqual(self.wiki_page1.parent_id, parent_before)
+
 @pytest.mark.enable_bookmark_creation
 class TestYWebsocketToken(OsfTestCase):
 
diff --git a/addons/wiki/views.py b/addons/wiki/views.py
index ef213addf82..bcf8b905095 100644
--- a/addons/wiki/views.py
+++ b/addons/wiki/views.py
@@ -93,6 +93,10 @@
     message_short='Invalid request',
     message_long='The requested version of this wiki page does not exist.'
 ))
+WIKI_INVALID_PARENT_ERROR = HTTPError(http_status.HTTP_400_BAD_REQUEST, data=dict(
+    message_short='Invalid parent wiki',
+    message_long='Parent wiki page does not exist on this project.',
+))
 
 WIKI_IMPORT_TASK_ALREADY_EXISTS = HTTPError(http_status.HTTP_400_BAD_REQUEST, data=dict(
     message_short='Running Task exists',
@@ -1453,7 +1457,10 @@ def _bulk_update_wiki_sort(node, sort_id_list, sort_num_list, parent_wiki_id_lis
         parent_wiki_id = parent_wiki_id_list[idx]
         setattr(page, 'sort_order', sort_order_number)
         if parent_wiki_id is not None:
-            parent = WikiPage.objects.get(guids___id=parent_wiki_id)
+            # Same-node only; global guid lookup would allow cross-project parents.
+            parent = WikiPage.objects.get_for_node(node, id=parent_wiki_id)
+            if parent is None:
+                raise WIKI_INVALID_PARENT_ERROR
             setattr(page, 'parent', parent)
         else:
             setattr(page, 'parent', None)