And they implemented it as strictly opt in (they ask before installing it), and fully user controlled:

"Firefox downloads and enables the Google Widevine CDM on demand, with user permission, to give users a smooth experience on sites that require DRM. The CDM runs in a separate container called a sandbox and you will be notified when a CDM is in use. You can also disable a CDM and opt out of future updates by following the steps below. Once you disable a CDM, however, sites using this type of DRM may not operate properly."

> If they didn't fold, they'd just lose more users to other browsers.

They rather lost a unique selling point. Not implementing EME/DRM is a form of protection of the user against malware.

So what was their option? Refusing to implement DRM (as opt-in) would mean that the ignorant user wouldn't be able to see Youtube videos anymore. The result would be that these users would move over to Chrome, Safari or Edge. There was no alternative.

They make EME-free builds. e.g. http://download.cdn.mozilla.net/pub/firefox/releases/55.0/

> They make EME-free builds. e.g. http://download.cdn.mozilla.net/pub/firefox/releases/55.0/

A well-hidden build of Firefox to silence the people who accuse the Mozilla Foundation of betraying their principles...

Mozilla is very upfront about the fact that it goes against their principles. https://hacks.mozilla.org/2014/05/reconciling-mozillas-missi... Anyway it's opt-in, it's easy to uninstall the one CDM it comes with, and it's fairly easy to stop it from even asking about downloading CDMs. The EME-free build just does all of that for you up front.

It is opt-in AFAIK.

There is no option I have to opt in whether I want a malware interface (EME) installed in my browser or not.

Yes, there is an option, and it has been linked repeatedly in these threads. The irony being, of course, that if Firefox didn't yield to the other browser vendors in implementing EME they wouldn't have the marketshare to keep development going, which means there would be zero browsers rather than one that make it trivial to forgo DRM.

What makes EME a malware interface?

DRM is malware (I don't seriously believe I have to explain why) - so EME is a malware interface.

I'm completely unfamiliar the entire discussion (I've just ignored it in the past), and I don't actually know why you think that. Could you elaborate?

A EME module is basically a proprietary closed source plugin just like silverlight and flash and shares the same potential security issues.

That's a gross oversimplification: Flash and Silverlight were rich platforms with complexity on the same order as the entire browser. EME has a much narrower interface which provides stream decryption – it doesn't even have the video codec, whereas Flash/Silverlight had complex video, audio, image, PDF, font, etc. implementations with a long history of exploits.

This really matters because so many of those exploits relied on other features to actually run the payload. Not having any of those in the first place is a big attack surface reduction, even if the politics are legitimately debatable.

It makes your computer stop responding to your commands in a bunch of ways.