I've got three problems which seem interconnected, but I can't figure out how to fix them. They all occur only in Firefox.
1. I can't log in to the WP admin panel. I enter my password, the page just reloads.
2. Same thing happens for my password protected pages. Enter the password, page just reloads.
3. I've got a "Join our mailing list" popup which is supposed to appear only once a week, but with this problem appears on every page load.
The most straightforward problem is the login issue. I've tried disabling all plugins, I've tried changing my theme. Even more puzzling is that I'm running an identical beta site on the same WP version that does not have this problem.