With the Tor browser update to version 7.0 [which is now based on Firefox 52.1.2], a bunch of changes have been made. The full list is available here https://blog.torproject.org/blog/tor-browser-70-released
But the perhaps most noticeably change is that you now get a warning when you go to the login or register page of hidden services [i.e.onion sites]. The warning is intended to warn users to not enter their login credentials on sites that are not secured through https. This is the case for nearly all hidden services, so you get that warning.
However while you really should not enter password on sites only available through http, the Tor network naturally provides end to end encryption when using hidden services. So your connection is still secure despite not using https. Please do not make new posts about this. If you see a post about it, please post a link to this thread in the comments.
Market admins: please include a short explanation for the warning on your login and register pages too, so users know that this is nothing they have to worry about.
Thanks for the update seen way to many post about kids freaking out remember it's summer time so we have all the rookies here