Logging in to websites using mainstream IDs (Google/Facebook/Github etc.) by means of OAuth (or similar) has nowadays become a feature that people expect.
Not that long ago the corresponding user experience included popups asking if the website should be allowed access the user's data from the ID provider. But today even that is no longer a norm: you can login with just a single click (for example, logging in to travis-ci.com with GitHub account).
Setting aside legal limitations (GDPR etc.), is it technically possible for websites to silently attempt to log visitors in with a range of ID providers in order to figure out who is visiting and grab whatever data is grabbable from those providers?
In other words, when I browse websites while logged in to say Facebook, are they technically able to log me in behind the scenes and see my name and whatever Facebook lets them see?