The ForceLogin Plugin comes bundled with OctoPrint (starting with version 1.3.10). It removes the anonymous read-only access that up until 1.3.10 was standard when accessing OctoPrint instances without being logged in and instead forces users to log in if they want to get any kind of information from OctoPrint.
Keep in mind that OctoPrint does not manage your webcam, it merely embeds it. If you have a webcam, it will still be accessible to users who are not logged in under its (guessable) URL. If you need to restrict access to your webcam, you’ll need to find a way to do so directly on the webcam server which - again - is not OctoPrint itself.
If you want back the old behaviour of allowing anonymous read-only access to your OctoPrint instance, disable the ForceLogin Plugin in OctoPrint’s plugin manager.
The source of the ForceLogin plugin is bundled with OctoPrint and can be found in
its source repository under