I don't think this is cached page, because this problem appear more and more even after changing pages and login/logout operations. I have try set mediawiki_mw__session expiration time the same as in other cookies. So, I have changed includes/GlobalFunctions.php in 2854, where I set first parameter to $wgCookieExpiration instead of 0 Also i change session name by set $wgSessionName variable in my LocalSettings.php I have really not tested, but I think this have fix my problem.