Here is a list of cookies squarespace currently drops and their description:
JSESSIONID- This is a Session-specific cookie for identification.
Crumb- This works with JSESSIONID to prevent cross-site request forgery.
Secureauthtoken- This is the main token dropped on SSL to identify the unique ID of the member account.
Securedirect- This cookie is dropped on non-SSL connection for the purpose of redirecting to SSL.
SS_MID- This cookie identifies a unique visitor. No visitor information is stored except a unique ID dropped on visitors to the site.
ss_cid- This is cookie is used to identify a unique user for Squarespace Metrics. The value assigned is a random GUID, and no personally identifying information is associated with this cookie. It’s purpose is to determine uniqueness of the user (unique visitor). This cookie expires after 2 years.
ss_cvisit - This cookie is used to identify a user’s session (visit). The value assigned is the timestamp of the initial page view for a session. This does not collect personally identifying information. This cookie expires after 30 minutes.
_utma, _utmb, _utmc, _utmz (Google Analytics)- We use this cookie to track traffic in aggregate on Squarespace marketing sites such aswww.squarespace.com. Customers use to get stats on visitors. No personally identifying information and only anonymous tracking to determine unique visitors.
PRUM_EPISODES (Pingdom)- This Cookie is for tracking performance (page load time, etc). Same bucket as Google Analytics in regards to anonymous monitoring.