On June 24th at 11.57 UTC we received an internal report that the Navigation Bar on www.hotjar.com was not visible.
We were running an experiment to try out a new Navigation Bar for the entire website. In certain instances of users using Firefox this was hidden.
Firefox uses a technique called Enhanced Tracking Protection, which is not switched on by default. When this had been switched on, or a user was running a Private window, our experiment settings failed to load and the Navigation Bar wouldn't be displayed.
We will hold an internal postmortem to identify ways to prevent it happening again.