IMO this is a more serious issue.Can someone confirm the issue?
Attached a test-portlet-war.
2. Login as John, save a User-Preference with test-portlet
3. Login as Mary, save a User-Preference with test-portlet
=> John now sees the User-Preference of Mary and viceversa.
UserPref.war 4.1 K
Can you file a Jira please ?
Someone may have a look today on this issue