Do not allow a Site Administrator user to add users to groups that have

the Manager role

src/plone/restapi/services/groups/update.py

@@ -1,5 +1,7 @@
+from AccessControl import getSecurityManager
 from plone.restapi.deserializer import json_body
 from plone.restapi.services import Service
+from Products.CMFCore.permissions import ManagePortal
 from Products.CMFCore.utils import getToolByName
 from zExceptions import BadRequest
 from zope.component.hooks import getSite
@@ -34,6 +36,10 @@ def __init__(self, context, request):
         super().__init__(context, request)
         self.params = []
 
+    @property
+    def is_zope_manager(self):
+        return getSecurityManager().checkPermission(ManagePortal, self.context)
+
     def publishTraverse(self, request, name):
         # Consume any path segments after /@groups as parameters
         self.params.append(name)
@@ -57,6 +63,9 @@ def reply(self):
         if not group:
             raise BadRequest("Trying to update a non-existing group.")
 
+        if not self.is_zope_manager and "Manager" in group.getRoles():
+            return self.reply_no_content(status=403)
+
         roles = data.get("roles", None)
         groups = data.get("groups", None)
         users = data.get("users", {})

src/plone/restapi/tests/test_services_groups.py

@@ -44,6 +44,20 @@ def setUp(self):
     def tearDown(self):
         self.api_session.close()
 
+    def set_siteadm(self):
+        siteadm_username = "siteadm"
+        siteadm_password = "siteadmpassword"
+        api.user.create(
+            email="[email protected]",
+            roles=["Site Administrator"],
+            username=siteadm_username,
+            password=siteadm_password,
+        )
+        self.api_session = RelativeSession(self.portal_url, test=self)
+        self.api_session.headers.update({"Accept": "application/json"})
+        self.api_session.auth = (siteadm_username, siteadm_password)
+        transaction.commit()
+
     def test_list_groups(self):
         response = self.api_session.get("/@groups")
 
@@ -173,3 +187,14 @@ def test_delete_non_existing_group(self):
         transaction.commit()
 
         self.assertEqual(response.status_code, 404)
+
+    def test_siteadm_not_add_user_to_group_with_manager_role(self):
+        self.set_siteadm()
+        payload = {
+            "users": {TEST_USER_ID: True, SITE_OWNER_NAME: False},
+        }
+        self.api_session.patch("/@groups/Administrators", json=payload)
+        transaction.commit()
+
+        administrators = self.gtool.getGroupById("Administrators")
+        self.assertNotIn(TEST_USER_ID, administrators.getGroupMemberIds())