Explanation:
Enhanced Tracking Protection in a Firefox Private Window (or Never Save History) blocks the loading of "https://squarespace.zendesk.com/auth/v2/host/without_iframe.js" (from https://support.squarespace.com/hc/en-us/signin) which is important for getting the cookies of an already logged in user. Since they are not set but javascript knows that they should be, it repeatedly attempts to get them.
Details:
When the appropriate cookies aren't submitted in a request for a help article, the HTML response includes:
<script type="text/javascript">
HelpCenter.user = {"identifier":"...","email":null,
instead of
<script type="text/javascript">
HelpCenter.user = {"identifier":"...","email":"youremail@example.com",
Then in one of the theme.zdassets.com js files (relevant lines extracted):
(variable i comes from https://login.squarespace.com/api/1/login/auth-status)
if (u = window.HelpCenter.user).email !== i.email
t.next = 16;
case 16:
(s = xe.a.getSignInHref()) ? window.location.href = s
So as a workaround (to avoid changing my browser settings) I get it to take a different path so that I can initiate the request for cookies myself:
if (r = window.ZD_SSO_SETTINGS.internal, !at.a.isSsoEnabled()) {
t.next = 25;