TYPO3 Core

(related to 3976 but it seems to not be fully debugged):

if i have two domains (a.com and b.com) in 1 TYPO3 installation, and i make all editors login from the maln one (a.com), there is big problem previewing workspaces for pages under b.com

the preview lanches the right preview url https://b.com/typo3/mod/user/ws/wsol_preview.php?id=642

but since the user is logged into a.com, they get "page not found" on he workspace preview of b.com

a SOLUTION to this is to aks editors to make a separate login into b.com/typo3 (so it sets b.com cookie), then the preview works.

i tried to manage the $TYPO3_CONF_VARS['SYS']['cookieDomain'] configuration, setting it also to

$TYPO3_CONF_VARS['SYS']['cookieDomain'] = '/\.(a|b)\.com$/';

but it seems to have no effect

any clues?

i could sponsor 50 euro for this debug! (i already spent 5 hours on it ... :(

(issue imported from #M11351)