I just ran a some browser tests against Beta Wikidata, which resulted in an email warning about a “Login to Wikidata as Lucas Werkmeister (WMDE) from a device you have not recently used”. That email includes a “help” link with the following URL:

https://mediawiki.org/wiki/Help:Login_notifications?markasread=34740&markasreadwiki=wikidatawiki

I’m not sure where I am supposed to mark that notification as read – I don’t see it on Beta versions of Wikidata, Meta, or English Wikipedia – but it can hardly be in the production cluster (or so I hope). That URL actually scared me because I first thought the login was in the production cluster for some reason – I had to check the sender (wiki@wikimedia.beta.wmflabs.org) to see that it really was a Beta thing.