diff --git a/CHANGES.rst b/CHANGES.rst
index 40d13c648..317846d2a 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,5 +1,26 @@
+Changes in synapse v0.28.1 (2018-05-01)
+=======================================
+
+SECURITY UPDATE
+
+* Clamp the allowed values of event depth received over federation to be
+  [0, 2^63 - 1].  This mitigates an attack where malicious events
+  injected with depth = 2^63 - 1 render rooms unusable.  Depth is used to
+  determine the cosmetic ordering of events within a room, and so the ordering
+  of events in such a room will default to using stream_ordering rather than depth
+  (topological_ordering).
+
+  This is a temporary solution to mitigate abuse in the wild, whilst a long term solution
+  is being implemented to improve how the depth parameter is used.
+
+  Full details at
+  https://docs.google.com/document/d/1I3fi2S-XnpO45qrpCsowZv8P8dHcNZ4fsBsbOW7KABI
+
+* Pin Twisted to <18.4 until we stop using the private _OpenSSLECCurve API.
+
+
 Changes in synapse v0.28.0 (2018-04-26)
-===========================================
+=======================================
 
 Bug Fixes:
 
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 4924f44d4..f31cb9a3c 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -16,4 +16,4 @@
 """ This is a reference implementation of a Matrix home server.
 """
 
-__version__ = "0.28.0"
+__version__ = "0.28.1"
diff --git a/synapse/util/logformatter.py b/synapse/util/logformatter.py
index 59ab3c696..3e42868ea 100644
--- a/synapse/util/logformatter.py
+++ b/synapse/util/logformatter.py
@@ -32,7 +32,7 @@ class LogFormatter(logging.Formatter):
         super(LogFormatter, self).__init__(*args, **kwargs)
 
     def formatException(self, ei):
-        sio = StringIO.StringIO()
+        sio = StringIO()
         (typ, val, tb) = ei
 
         # log the stack above the exception capture point if possible, but
diff --git a/tests/appservice/test_scheduler.py b/tests/appservice/test_scheduler.py
index e5a902f73..918169277 100644
--- a/tests/appservice/test_scheduler.py
+++ b/tests/appservice/test_scheduler.py
@@ -17,6 +17,8 @@ from synapse.appservice.scheduler import (
     _ServiceQueuer, _TransactionController, _Recoverer
 )
 from twisted.internet import defer
+
+from synapse.util.logcontext import make_deferred_yieldable
 from ..utils import MockClock
 from mock import Mock
 from tests import unittest
@@ -204,7 +206,9 @@ class ApplicationServiceSchedulerQueuerTestCase(unittest.TestCase):
 
     def test_send_single_event_with_queue(self):
         d = defer.Deferred()
-        self.txn_ctrl.send = Mock(return_value=d)
+        self.txn_ctrl.send = Mock(
+            side_effect=lambda x, y: make_deferred_yieldable(d),
+        )
         service = Mock(id=4)
         event = Mock(event_id="first")
         event2 = Mock(event_id="second")
@@ -235,7 +239,10 @@ class ApplicationServiceSchedulerQueuerTestCase(unittest.TestCase):
         srv_2_event2 = Mock(event_id="srv2b")
 
         send_return_list = [srv_1_defer, srv_2_defer]
-        self.txn_ctrl.send = Mock(side_effect=lambda x, y: send_return_list.pop(0))
+
+        def do_send(x, y):
+            return make_deferred_yieldable(send_return_list.pop(0))
+        self.txn_ctrl.send = Mock(side_effect=do_send)
 
         # send events for different ASes and make sure they are sent
         self.queuer.enqueue(srv1, srv_1_event)
diff --git a/tests/storage/test_event_push_actions.py b/tests/storage/test_event_push_actions.py
index 575374c6a..9962ce8a5 100644
--- a/tests/storage/test_event_push_actions.py
+++ b/tests/storage/test_event_push_actions.py
@@ -128,7 +128,6 @@ class EventPushActionsStoreTestCase(tests.unittest.TestCase):
         yield _rotate(10)
         yield _assert_counts(1, 1)
 
-    @tests.unittest.DEBUG
     @defer.inlineCallbacks
     def test_find_first_stream_ordering_after_ts(self):
         def add_event(so, ts):
diff --git a/tests/util/test_logformatter.py b/tests/util/test_logformatter.py
new file mode 100644
index 000000000..1a1a8412f
--- /dev/null
+++ b/tests/util/test_logformatter.py
@@ -0,0 +1,38 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import sys
+
+from synapse.util.logformatter import LogFormatter
+from tests import unittest
+
+
+class TestException(Exception):
+    pass
+
+
+class LogFormatterTestCase(unittest.TestCase):
+    def test_formatter(self):
+        formatter = LogFormatter()
+
+        try:
+            raise TestException("testytest")
+        except TestException:
+            ei = sys.exc_info()
+
+        output = formatter.formatException(ei)
+
+        # check the output looks vaguely sane
+        self.assertIn("testytest", output)
+        self.assertIn("Capture point", output)