Freezing browser with Mosquitto 1.5

Code that ran fine with mosquitto 1.4.15 stopped working with mosquitto 1.5 and freezes the browser.
The issue can be replicated by running the sample code from the project main page.
In the development console thousands of executions of the 'onConnect' method can be seen. It seems some out-of-control loop is freezing up the browser.

Run the sample code from the project main page with Mosquitto 1.5, then inspect the development console for repeated executions of onConnect. Compare the behavior with Mosquitto 1.4.15. Done means the sample no longer freezes the browser and onConnect no longer executes in an uncontrolled loop.

Written by the indexing model from the issue text.