Disabled. Same reason as
"Extensions are just part of the problem. Any form of browser integration can create security holes. After all,
that’s the point of encryption–to keep that traffic private. To get around this limitation, some antivirus programs effectively perform a “man-in-the-middle” attack so they can monitor what’s actually going on over an encrypted connection. These work an awful lot like Superfish, replacing certificates with the antivirus’s own. The MalwareBytes blog
explained avast!’s behavior here.
This feature is generally just an option in the antivirus program itself, and not part of a browser extension, but it’s worth discussing all the same. For example, Avast’s SSL-interception code contained an
easily exploitable security hole that could be used by a malicious server. “At least get an intern to skim your before shipping it,” tweeted Ormandy after discovering the problem. It’s one of those bugs that Avast, a security company, should have caught before shipping it to users.
As he argued in following tweets, this sort of
man-in-the-middle code just adds more “attack surface” to the browser, giving malicious sites another way to attack you. Even if the developers of your security program are more careful, features that tamper with your browser are a lot of risk for not much reward. Your browser already contains anti-malware and anti-phishing features, and search engines like Google and Bing already attempt to identify dangerous websites and avoid sending you there."