Older UGC site makers have this issue when posting such sites as subdomains. Newer ones put user stuff on subdomains of another top level domain. Mitigations in

Older UGC site makers have this issue when posting such sites as subdomains. Newer ones put user stuff on subdomains of another top level domain. Mitigations include having login on a separate domain and use oauth to yourself. :) There is actually a list of such sites that Firefox has (had? haven’t been in the space in a while) that they could use for various reasons. Like treating the tumblr.com domain as an international domain (co.uk) which Google search would do as well.