Accessing http://meta.m.wikimedia.org/wiki/Main_Page on desktop (Note: not HTTPS) shows the following notification at the bottom of the page:
Central login
You are centrally logged in. Reload the page to apply your user settings.
However, when refreshing, the same notification is again. The user never ends up actually being logged-in.
Presumably the actual login session is established on HTTPS, but the user has no way of knowing that and there is no path through the UI to get there.
EDIT: After trying over HTTPS, the same happens. So it's not related to being on HTTP or HTTPS. Accessing https://meta.m.wikimedia.org/wiki/Main_Page results in the same notification being shown. Refreshing doesn't make it go away. It keeps coming back.
Cookie jar:
Name Domain Path Expires Size HttpOnly Secure First-Party Value ------- GeoIP .wikimedia.org / Session 31 *:*:*:*:v4 WMF-Last-Access meta.m.wikimedia.org / 2015-07-02T12:00:02.833Z 26 ✓ *-May-2015 _ga .wikimedia.org / 2017-04-12T18:06:51.000Z 29 GA1.2.**.** centralnotice_buckets_by_campaign meta.m.wikimedia.org / 2015-07-01T21:59:00.000Z 132 %7B%22wl**40%7D%7D
The Network tab is showing a ton of requests being made in the background. A total of over 70 requests are made in relation to central auth every page view.
createSession?token=<hash>&type=script&proto=https validateSession?token=<hash>&wikiid=metawiki&type=script&proto=https setCookies?type=script&proto=https toolslist?returnto=Main_Page&returntoquery= start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki start?type=1x1&from=metawiki refreshCookies?type=1x1&wikiid=metawiki&proto=https load.php?debug=false&lang=en&modules=mediawiki.notification&skin=minerva&version=19700101T000000Z&* checkLoggedIn?wikiid=enwikiquote&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=enwikisource&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=enwikinews&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=mediawikiwiki&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=enwiki&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=enwikibooks&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=incubatorwiki&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=commonswiki&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=enwikiversity&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=specieswiki&proto=https&type=1x1&from=metawiki checkLoggedIn?wikiid=enwiktionary&proto=https&type=1x1&from=metawiki createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https checkLoggedIn?wikiid=wikidatawiki&proto=https&type=1x1&from=metawiki createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https checkLoggedIn?wikiid=enwikivoyage&proto=https&type=1x1&from=metawiki createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwikibooks&type=1x1&from=metawiki&proto=https createSession?token=<hash>&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=incubatorwiki&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwikiquote&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwikinews&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwikiversity&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=mediawikiwiki&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwiktionary&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=specieswiki&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwiki&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwikisource&type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=commonswiki&type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=enwikivoyage&type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https validateSession?token=<hash>&wikiid=wikidatawiki&type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https setCookies?type=1x1&from=metawiki&proto=https