Works exceptionally well. If there is a cookie, it will be listed, and it can be allowed.
The only problem I have with it is that it does not have any UI for quickly-redirecting sites. This is happening more and more frequently that an array of sites bounce me in rapid succession from one to another, each requiring cookies, and this tool flashes on them but does not allow to stop and allow cookies. On such sites it has to be disabled completely, which totally defeats the purpose.
I still give it 5 stars because otherwise it does exceptionally well!

I've been using this extension since the legacy ones stopped working and I only had one problem today logging into my router. So, that's a few years of perfect performance. I wanted an extension that would let me allow/block cookies on a per-domain basis, including third party cookies and would remember my choices between sessions. I imagine this is what most regular users need, just a simple and effective cookie control. I don't see any other extension out there that does that. If you need developer's tool look elsewhere, and read the description before installing. For users that want to clear the cookies already set, just use the Clear Recent History option. Overall, I am extremely grateful for the effort that Craig Miskell is putting in the development of this extension and I'm going to submit a suggestion for it to become recommended. I hope this draws more people to take a look at it. Thank you, sir.

Seit Jahren suche ich einen Ersatz für mein gutes, altes Cookie-Monster. Stunden verbrachte ich damit, ein ähnliches Add-On zu suchen. Endlich! Jemand hat es nachprogrammiert. Ganz lieben Dank Craig!
Craig antwortet sogar auf Anfragen und zu meiner großen Freude ist geplant, eine Backup-Möglichkeit ebenso einzubauen, wie ein Auto-Import der erlaubten Cookies aus FF. Ich freue mich darauf!

translated to English:
Since years I search for an replace for my good old "Cookie-Monster". I spent hours in searching something like it. Finally: Somebody programmed a copy-add-on of its funktions. Many Thankys, Craig! Craig answers even to mails. To my excitement it is planned, to add a backup-solution as well as an auto-import of the cookie settings. I am excited about!

Great! Now all it needs is to show status on the button.

if you want to control who can write cookies to your machine, this is the extension to use - fantastic!

amazing !!!

I echo other reviewers where they mention that this addon allows DEFAULT BLOCK (with exceptions) for cookies. No other addon gives us back cookie control like this. THANK YOU Craig Miskell.

Some features which I hope get added soon :)
1. The cookie toggles do not show up when browsing in Private mode. Please fix that if possible.
2. Possible to extend this addon to Firefox for Android? I would love to be protected across my devices!

This addon does exactly what it says it does and I love it for its simplicity. However, there are 2 things that keep me from giving it a 5 star rating:
1. The icon is just a static (and IMO ugly) image. It would be better to use the icon to indicate blocked cookies (red), blocking some/3rd party orange, and green allowing all. A material design, outline cookie would be really nice and blend in with FF own icons.
2. When changing cookie settings (ie, allowing some), a page requires a refresh. The addon does not trigger a page refresh, nor does it provide any settings to control or show a warning.

Otherwise a very nice and simple addon that does what its supposed to do. Thanks and keep up the good work!

This is as close as we're going to get to something that even closely resembles the old "ask me every time" option for cookies in that it will actually block cookies from being set for denied websites and the whitelist/blacklist stays between sessions. Other cookie managers still allow "blocked" cookies to be set on your computer, only deleting them after a period of time or the session closes, CookieMaster does what it's supposed to and it's super simple. I do wish I could set some websites to only set cookies for a session instead of just allow/block, but I'm totally happy with the way this is right now.

Finally a replacement for the great but unfortunately gone CookieMonster addon. I don't have much experience with this addon yet but it seems to do its job and is pretty easy to use.
However when you set a cookie permission, the addon keeps this decision permanent (that means the cookie allowance is still set if you close Firefox and reopen it) unless you delete the permission again in the preferences menu or deselect the permission if you go to the particular website again → That's a feature from CookieMonster which I would really like to be resurrected, namely also giving the option of allowing cookies only on a per-session basis. If this feature is implement, I'll gladly bump up my rating to a 5.

Easy to use, when it works it does so transparently and with no disruption. The only problem is that it doesn't always work. It always allows some cookies even when all are banned. It's not always the same cookies, it's almost a random assortment. But after every browsing session I need to go delete the cookies that it let through. I still use it because the alternatives are even worse.

If it actually blocked all the cookies it's supposed to, this would be a 5 start rave review.

Useless.

1. This add-on cannot detect the currently set cookies. Only after reload will be cookies detected.

2. This add-on prevents setting of cookies even in the "Allow All" mode. You have to enable each domain separately.

It is hard to find any realistic scenario when this add-on might be needed. That is why it is useless to me.

Uninstalled.

Update 06.01.2019:

Regarding reloading: OK, I could accept it, if there was a hint that one has to clean up all cookies by himself and reload page.

Regarding "there is no realistic scenario": Of course there many such scenarious. Here is just one example. You disable some cookies to remove some advertising or tracking . On many sites this blocks also some functionality like commenting or sharing via Twitter or Facebook. In most cases you don't care about this. But sometimes you want to write a comment or share the content. To enable this, you have to enable blocked cookies. You don't want to spend hours analyzing what cookie is responsible for this. You just enable all cookies (and accept tons of advertising), reload page, write a comment of share the content, then disable all cookies (from the black list) again.
There are many similar scenarios, when you want temporarily enable some cookies, but don't want to waste time analyzing which ones you need. You just enable all blocked cookies, do what you need, then again disable all blocked cookies.

I want to like this, it's just what I need to replace the old CookieMonster (RIP). The problem is it doesn't actually delete any cookies! They are all still there in the Preferences window even though CookieMaster shows they aren't allowed.

Good extension to replace cookieSafe, which is no longer maintained. Also works on Firefox 57 while cookieShield does not. I would have put 5 stars if an option "allow for the session" had been present. This could be a good improvement. Thanks to the author for making our life easier. A tip: this module works when cookies are allowed in the firefox options.