Geolocation request error while using the current user location button

When hitting the "Show current location" button, I get the following error in the JavaScript console, at line number 1732 of leaflet.js:

A Geolocation request can only be fulfilled in a secure context.

The line raising the error seems to be the following:

return t.watch ? this._locationWatchId = navigator.geolocation.watchPosition(n, o, t)  : navigator.geolocation.getCurrentPosition(n, o, t),

Environment: Firefox 67.0b10 (64-bit)