How do I allow commenting in Youtube (through Google+) if I have third-party cookies disabled?

Question

Ever since YouTube required Google+ to comment, I had been unable to comment and vote on comments on YouTube videos using my Firefox browser, even though I have a Google+ account linked to my YouTube account. Clicking on a comment box opens up a new tab with an URL that looks something like https://plus.google.com/u/0/wm/4/up/?type=st&client=7&gpsrc=gpfw0&parent=https%3A%2F%2Fapis.google.com&proxy=I1_...&rsz=1&hl=en_US, then that tab get closed and I get returned to the YouTube page I am viewing, still unable to comment.

Upon further troubleshooting, I realized that this is due to having 'accept third-party cookies' set to 'Never' in Firefox' settings. Allowing third-party cookies for all sites (setting it to 'always') makes me able to comment in YouTube normally.

I still would prefer to disable third party cookies for all websites and just make an exception for YouTube, though. So, I tried making an exception for 'YouTube.com' and 'plus.google.com' in Firefox options » Privacy » History » Exceptions and have set it to 'allow', but I still can't comment.

EDIT - further research info: Adding 'google.com' in the cookie settings exception fixes this issue but this will also allow third party cookies for all google.com websites. I'd rather not do that to prevent Google from tracking me more than it already does.

How do I configure Firefox to allow commenting and comment voting in YouTube while still mostly not allowing third-party cookies by default? Are there extensions that can allow this in such a way that third-party cookies are still mostly disabled (just allow it at times I would like to comment in YouTube, or make an exception for YouTube)?

I'm using Firefox 25.0.1 on Windows 7.

Answer 1

The new YouTube commenting system uses Google+. In order for commenting and comment voting to work, you need to allow third-party cookies from 'apis.google.com' to set cookies in 'youtube.com'.

To do this in Firefox, go to Options » Privacy » History » Exceptions, add apis.google.comand set it to 'allow for session'. This should allow you to comment on YouTube with Google+.