problematic dot in url

I got a url parameter which contains 3 dots named token. suppose it is 'boo.foo.joo'. my controller's method which is supposed to handle request only takes the first two parts ('boo.foo'). however I can see the remaining part in my request.response_ext. what is response_ext? is this behavior coming from my web framework or is it a universal convention?

from tg import request

def recover_password(self, token):
    print(token) # outputs > 'boo.foo'
    print(request.response_ext) # outputs > '.joo'