Some people might downvote me for this (as happened before) but I have cookies disabled by default. Only if I need to interact with a website I am ok with traces and I allow cookies for that domain via the Cookie Controller add-on.
Now the strange thing: thumbor requires cookies in order to serve images. It requires quite lax settings since allowing cookies for thumborg.org as first party only doesn't suffice. I need to accept all possible cookies, I think because one offending cookie has domain .thumborg.org.
I think serving images should not depend on cookies, or is there a good reason?