I've been getting the above message in every post for a couple of weeks now, but only while being logged in. It occurs consistently on different (Windows) computers and with different browsers (Chrome version 85.0.4183.83, Edge).
Here's a screenshot:

In the HTML source code it says:
class="lia-widget-not-found"
Do I need to install or update something to get that "lia widget" or is it perhaps blocked by my antivirus software?