Ever since I updated my OC to v. 9.1, every user has had to login every time they close a browser. Now, I do have a 2FA (Google Authenticator) enabled, but only for the admin user. The behaviour in question affects everyone - but only in the browser, obviously - using an an app (say OC News reader on Android) is fine.
None of the browsers is set to clear cookies on exit, no other websites which preserve logins are affected. Tried under Chrome, Firefox and Opera.
Steps to reproduce
1. Open a browser (i.e. Google Chrome)
2. Login to OC
3. Do stuff
4. Close browser
5. Re-open browser and OC page
The requested page loads straight away
Login prompt appears.
Operating system: Ubuntu 14.04
ownCloud version (see ownCloud admin page): 9.1
Updated from an older ownCloud or fresh install: 9.0.1
ownCloud log (data/owncloud.log, see https://central.owncloud.org/t/how-to-find-webserver-or-oc-logfile-enable-php-logfile/808):
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): 2FA, but only for the admin user
Integrity status for oC9+
No errors have been found.