Chris Blizzard posts in favor of the new arrangement, and points to an interesting post by Johnathan Nightingale explaining Mozilla’s position. Yes, agreed, Jonathan’s post is a good read, but the salient point is that the new UI is just awful from an average non-technical user’s perspective.
The extra clicks and somewhat abnormal flow (e.g. the need to click a button in the dialog to fetch the certificate) make it harder for the user to understand how to successfully add the exception. You might say that some false positives (i.e., users who fail to access a site that they really actually do want to access) is better than a user succumbing to a MITM attack, but I’m not sure I’d agree.
Equally importantly, the error messages make no distinction between the potential severity of the various SSL errors. For example, I’d say a self-signed cert on a site that you’ve never visited before is fairly low-risk. But a self-signed cert on a site that used to have a trusted cert would be a huge red flag. Domain mismatches and expired certs would fall somewhere in between. It’s hard for the average user to make an informed decision on risk/severity if they were to encounter both of these situations because the error messages and dialogs look exactly the same.
Addressing Johnathan’s main point about self-signed certs and level of security: as a highly technical/advanced user, I personally can say that, in the vast majority of instances where I encounter a self-signed cert, I really do just care about the encryption, and I don’t particularly care about the identity verification of the site that a trusted cert could offer. Now, Firefox probably shouldn’t use me as an example as a target user that needs protection, but that’s a data point nonetheless. I don’t care for things like: Bugzilla installations, my blog, accounts at sites like identi.ca, Twitter, Slashdot (they don’t offer SSL at present, but if they did…), etc.
Pretty much the only time I do care are for financial institutions. And guess what? They’ve already decided that SSL as used for identity verification is useless! Most of them (I can only think of one that I use that hasn’t) have already implemented a “security image” system wherein I pick a random image that gets shown to me every time I log in. If a site claiming to be the site I want shows me an image I don’t recognise, I’ll know that the site is a fraud. Is it perfect? Probably not. But it’s orders of magnitude better then what SSL error dialogs offer.
And I guess that’s really it: as much as I hate the phrase, I really think that the SSL error dialogs are “a solution in search of a problem.” In the cases where I care about site spoofing, the sites themselves have already implemented a better solution. In the cases where I don’t care, well… I don’t care.