Add 1.5.10 information.

ChangeLog.txt

@@ -19,6 +19,20 @@ Clients:
 - Don't busy loop with `mosquitto_pub -l` on a slow connection.
 
 
+1.5.10 - 2020-08-19
+===================
+
+Security:
+- In some circumstances, Mosquitto could leak memory when handling PUBLISH
+  messages. This is limited to incoming QoS 2 messages, and is related
+  to the combination of the broker having persistence enabled, a clean
+  session=false client, which was connected prior to the broker restarting,
+  then has reconnected and has now sent messages at a sufficiently high rate
+  that the incoming queue at the broker has filled up and hence messages are
+  being dropped. This is more likely to have an effect where
+  max_queued_messages is a small value. This has now been fixed. Closes #1793.
+
+
 1.6.11 - 2020-08-11
 ===================
 

www/posts/2020/08/version-1-6-12-released.md

@@ -9,7 +9,7 @@
 .. type: text
 -->
 
-Mosquitto 1.6.12 has been released, this is a bugfix release.
+Mosquitto 1.6.12 and 1.5.10 have been released.
 
 # Security
 - In some circumstances, Mosquitto could leak memory when handling PUBLISH
@@ -21,6 +21,8 @@ Mosquitto 1.6.12 has been released, this is a bugfix release.
   being dropped. This is more likely to have an effect where
   `max_queued_messages` is a small value. This has now been fixed. Closes [#1793].
 
+The following fixes apply to 1.6.12 only.
+
 # Broker
 - Build warning fixes when building with `WITH_BRIDGE=no` and `WITH_TLS=no`.