For about the past week I have been unable to successfully use Firefox on MacOS with a number of WordPress sites. When I try to log in it says that cookies must be enabled, and when I check the cookies for the site it shows that they have not been set. There are also other parts of some sites that set cookies but these are not being set either.
I have seen this behaviour occurring now on a lot of sites that I manage, some at WP 3.6.1 and some at WP 3.7. At first I thought it was 3.7 causing the problem, then I thought it might be Firefox's database getting corrupted (as it has before in the past) so I cleared the cache & cookies in the hope that it would solve the problem.
Then it happened at home too over the weekend, so it's obviously not my installation of Firefox that is causing the issue.
Has anyone else noticed anything like this?
The sites all work perfectly in Safari and Chrome, so that really does suggest the latest update to Firefox might be the culprit.