This message is related to Firefox's Enhanced Tracking Protection feature. If I recall, there's no particular thing that triggers this message to appear, it's just a standard progress notification. Enhanced Tracking Protection is a feature that tries to stop websites from tracking you. This is no so much tracking in the traditional sense of a company trying to see your password. Rather, social media trackers are snippets of code that exist on many websites and they are able to track where you are going. For example, if you visit Website A and it has a share button for Facebook, that code is loaded from Facebook. Facebook can see that you've visited the website, whether or not you clicked the share button and whether or not you are logged in to Facebook. It's the same if you visit Website B and Website C, both of which also have share buttons. Using this method, Facebook would be able to map what you are visiting. This information is used for a variety of purposes. Firefox's Enhanced Tracking Protection feature essentially tries to stop loading that type of tracking content. So if you visit Website A, maybe you won't see a share button because Firefox has stopped the necessary code from loading. Of course, that's just an example using a company name that you are likely already familiar with. In the Firefox address bar, there's a shield icon on the left side. If you press that, you can see what type of content is being blocked on the current website and where it's coming from. Pressing the '''Protections Dashboard''' button will bring you to a screen with less specific statistics about what's been blocked on your browser over time. More information about this feature can be found on the [[Enhanced Tracking Protection in Firefox for desktop]] page.