Hello,
According to [1] and [2], Firefox 22 (release June 25, 2013) will change
the default third-party cookie policy: a third-party cookie will be
authorized only if there is already a cookie set on the third-party
website.
This would break most of the automatic login on sister projects on
Wikimedia websites, since the page just after the log in will no more set
cookies of sister projects, and you will have to manually log in to each
domain (of level
wikipedia.org, not of level
de.wikipedia.org) -- I tested
with Firefox 16.
What could be done to mitigate this effect? According to [1] Safari
already have this policy; is there some workaround already in place for
Safari users? I don’t see other solutions than displaying some warning to
the Firefox/Safari users (via JavaScript).
[1]
http://webpolicy.org/2013/02/22/the-new-firefox-cookie-policy/
[2]
https://developer.mozilla.org/en-US/docs/Site_Compatibility_for_Firefox_22
~ Seb35