Most/all topics have this. Can it be disabled? Maybe due to a resource used by Discourse?
It is probably blocking the share on facebook button. I suspect you see that icon in the corner because the element isn’t visible unless you click on the share button.
It happens on all discourse forums and I don’t think it is actually doing any facebook tracking. The facebook container blocks all access to facebook, tracking or not.
When non-Facebook sites add a “Like” button (a social plugin, in Baser’s terminology), visitors to those sites are tracked: Facebook gets their IP address, browser and OS fingerprint, and visited site.
In a blog post, Facebook’s product management director, David Baser, wrote that the company tracked users and non-users across websites and apps for three main reasons: providing services directly, securing the company’s own site, and “improving our products and services”.
“When you visit a site or app that uses our services, we receive information even if you’re logged out or don’t have a Facebook account.
Facebook often installs cookies on non-users’ browsers if they visit sites with Facebook “like” and “share” buttons, whether or not a person pushes a button. Facebook said it uses browsing data to create analytics reports, including about traffic to a site.
Baser explained that one of the services Facebook provides to websites and apps is Audience Network: a service that lets advertisers create ads on Facebook that show up elsewhere in cyberspace. Advertisers can also target non-users with a tiny but powerful snippet of code known as the Facebook Pixel: a web targeting system embedded on many third-party sites. Facebook has lauded it as a clever way to serve targeted ads to people, including non-members.