Cookies are cleared on every page navigation (on development)

Happens Only On The Development Environment

On an Ember + Ember-Simple-Auth (CookieStore) SPA with Rails + Devise on the backend I have the situation that every time I navigate somewhere (different URLs, reload on the same URL) the cookies are cleared by default and I can't find where this happens.

Once I reload the cookies that are sent to the backend are already cleared, which makes me guess that it's not Rails that's doing that.