Well, it's not an issue with Tor, because Tor is just the underlying transport -- it does not understand or think about the bytes that it helps you send back and forth to websites.

So you should be looking at Tor Browser, which is also included in Tails.

But it sounds to me like you are misunderstanding something. http client auth is used at far fewer than "all" web sites, for starters.

Are you saying this because you actually found a bug? Or because you went to some "how safe am I" website and it told you to be scared of the phrase "http authentication"? If it's the former, please open a ticket at https://bugs.torproject.org/