Is CSRF a threat if not using cookies?
CSRF isn't just protection against CORS AJAX. I could make a form on my site, and set the action to http://yoursite.com/account/delete. If a user submits my form, without CSRF on your site, the action would succeed. Or if you have things change on GET requests (shouldn't do that anyway), I could add this to my site:
<img src="http://yoursite.com/account/delete" />and the action would happen when my page loads.
Check out Flask-WTF or this snippet: http://flask.pocoo.org/snippets/3/
EDIT
From your comment:
Change the action of that page to a POST, and have it be accessed through a form instead of a link. If your link was:
<a href="{{ url_for('my_page') }}">Click Here</>Your form could be (using Flask-WTF, which you would need):
<form action="{{ url_for('my_page') }}" method="POST"> <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" /> <input type="submit" value="Click Here" /></form>