Subscription button visible to anonymous users

Problem/Motivation

The forum topic subscription button is visible and available to anonymous users, and there is no way to hide it from permissions

Steps to reproduce

I show the subscription button in forum topics through the "Subscription link" field in the "Manage Display" of the "Forum topic" content type. Then I visited the website without being logged in, and I see the button, which can be clicked and breaks the website, showing an text area with JSON information like
[{"command":"insert","method":"replaceWith","selector":"#forum-topic-subscription","data":"\u003Cp\u003E\u003Ca href=\u0022\/forum\/unsubscription\/node\/32\u0022 id=\u0022forum-topic-subscription\u0022 class=\u0022use-ajax btn btn-primary\u0022\u003EUnsubscribe from this forum topic\u003C\/a\u003E\u003C\/p\u003E","settings":null}]