The original issue was:
Error: "You are using a feature that requires $cookie_domain to be set, but it is not set in your settings.php (CKFinder is enabled in the Advanced profile"
Any help would be highly appreciated.
What's the ticket is actually about: comment #18 by anarcat
From what I understand by reading this issue, it's because CKFinder bypasses the normal Drupal bootstrapping.
I do believe, however, that relying on a variable that *may* be defined in settings.php is a bug in that context. If you expect Drupal variables, you expect Drupal to be bootstrapped. If you bootstrap Drupal the wrong way, you're headed for a bunch of trouble, period.
The way the fix was proposed in Aegir was to add this line to the settings.php template:
$cookie_domain = $_SERVER['HTTP_HOST'];
I object to this change (edit: this change in aegir) on the ground that this work is already done by conf_init() (as found by Steven) in Drupal core itself.
If CKFinder doesn't bootstrap Drupal properly, it should at *least* default $cookie_domain properly, in the exact same way as above. It shouldn't be put on the users' shoulders to do that work instead of the module fixing its bootstrap code.
It could even be possible to load includes/common.inc and fire up conf_init()...
(I took the liberty of changing the issue title and type, I hope that's okay.)