Additional Reading:
Cross Site Cookie Tracking, as the name indicates, cross site cookie tracking is a way of tracking that detects and follows users on their journey across different websites.
Other items that are affected by cross site data exchanges:
+ Data set by different scheme, http vs https but on the same domain.
+ Data set by forums.example.com vs
www.example.com. vs example.com
+ Current website data with data linked from a third-party. For example, Facebook, LinkedIn and Twitter 'share' and 'like' buttons are present on the vast majority of websites. Or even an incorrectly configured CDN for linked site assets.
If the latest version of a modern browser is impacting the functionality of a website, you may want to revisit your browser's "tracking protection" settings. Your issue may also be resolved simply by visiting the website directly, and not from within an "In Private/Incognito" window while attempting to configure your forum/script software. The majority of the people accessing those websites are connecting directly, without any customizations to their browsers at all.
An older version version of a browser (or one with less support) could be working for you because it does not support those security protections that you have enabled in a modern browser.
