MQTT message topics no longer published

Since yesterday June 9, 2021 @2100Z the MQTT API is no longer include any topics to the messages it’s publishing. Just its value.

Nothing has changed on our side. These have been production units for years now.
Network is not at fault. Devices are connected from all over the world.
The MQTT message broker is 100% operational and works fine with devices unrelated to Particle.io
Not a device issue, we have both Argon and Photon and all running either 1.5 or 2.X FW versions without any issues until then.

Anyone else witnessing the same behavior ?

Hi @philstrick - can you please open a Support ticket about this, with as much detail as you can (including description of the entire flow, some sample devices whose behavior we can track, an abstraction of your firmware we can use to reproduce the issue if possible)?

Absolutely. Will do.

Turns out to be a MQTT Mosquitto security update on our backend server which was pushed to the server on Wednesday 9 at 21:43 UTC. Exactly when we experienced the service outage.
Solved by upgrading external services: Mosquitto + Telegraf
case closed.