I've just upgraded to MW 1.28.0 and now when I purge a page (being logged in as WikiSysop) I am asked for a confirmation as if I was an anonymous user. I guess that there must be some new configuration setting introduced but there is no such mention in Manual:Purge or in what's-new pages.
Topic on Project:Support desk
In Manual:Purge there is a section "Requests must be confirmed".
Thanks, I had already read that but after you pointing out that again, I noticed a small reference https://gerrit.wikimedia.org/r/#/c/304157/ which eventually led me to https://phabricator.wikimedia.org/T135170 So I see that now purging must be confirmed by all (anonymous or not) unless you go via the API, or use some JS gadget.
So I mark this as solved and for more answers I may continue this talk in Phabricator.