Re: Double log-in: Possible security threat!
Okay, I checked into the cookie issue.
First, TikiWiki's default is broken. If nothing is set (which was the case for both the old and the new installation) it sends cookies for / which in 99% of all installation is wrong, I guess most admins will install into /tiki.
So the cookies are for the wrong directory anyway, by default it should always be set to the main Tiki directory. Setting the correct directories led to 6.7 LTS placing correct cookies - but now loggin in is defunct altogether, maybe I have to delete serverside caches.
On 1.9.8.3 most entries are correct, except for tz_offset which still came with the wrong directory. Maybe a serverside issue. too.