User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 Build ID: 20140914030209 Steps to reproduce: Enabled e10s as a participant in the Nightly build (9/14/14) by clicking "accept" to pop-up Actual results: Once enabled, first-party cookies don't work in Nightly and I can't log in to any sites as the message saying first-party cookies are needed shows up. Any active log-ins were logged out. Expected results: Able to log in on sites that require first-party cookies. (picture included uses facebook login as an example)

I would also like to include that with addons enabled/disabled makes no difference. List of addons: Adblock Edge Privacy Badger beta (direct from eff.org) https everywhere (direct from eff.org) DownloadThemAll! NoScript Omnibar Same issue occurs in Fedora 20 64-bit

courthicks: can you reproduce this bug in a clean Firefox profile or if you uninstall (not just disable) Privacy Badger? I've see some bugs with addons causing problems when they are installed, even when they are disabled. Scheduling for M3 milestone. We haven't been able to reproduce this problem yet, but it sounds bad.

I'm running OpenSuse 13.1 64-bit with KDE now also, I'll try Windows 7 Pro 64-bit and Fedora 20 GNOME 64-bit later when I'm home, but I thought I'd add this too. I did a fresh copy of Nightly (on the OpenSuse computer) and it loaded up my sync profile, but I started it up with addons disabled and then I removed them completely. I had to go to about:config to enable e10s since I didn't get the pop-up asking me to opt-in. I encountered the same issue where even with first party cookies enabled, I can't login to any websites because of first party cookie issues

Having cookies set to first party only or adding sites to the exceptions list currently breaks cookies in e10s, tracked in bug 1049299