Or in other words it is vulnerable.

China can (and probably does) issue a certificate that all Chinese browsers must install, they can then do MITM https using their certificate to sign the new versions.

Companies do this routinely BTW. Since it's their equipment, it's considered just fine. (But be aware of it if you are using a company computer.)

I've never seen or heard of this (at least across all browsers), so I find this unlikely.

"On Friday, March 20th, we became aware of unauthorized digital certificates for several Google domains. The certificates were issued by an intermediate certificate authority apparently held by a company called MCS Holdings. This intermediate certificate was issued by CNNIC."

Although there have been lots of concerns about CNNIC, I don't believe that the Chinese government currently either (1) routinely uses CNNIC to perform MITMs for censorship or mass surveillance purposes, or (2) purports to require UAs to trust CNNIC or another Chinese root in order to be used by Chinese users. I'm happy to be corrected if someone knows otherwise.

What's more dangerous, and much more likely, is that they might use forged certificates against specific individuals for a short period of time, for example, to intercept login credentials. The attack will go unnoticed as long as they also block the corresponding HPKP reporting URL (if the targeted site uses HPKP at all).

Hopefully the risk for the attacker from the two kinds of attack are gradually converging, due to pinning and especially Certificate Transparency.

Lots of people travel in and out of China with all sorts of computing devices. China does care about the reputation of their root and of their highly profitable electronic exports.

https://en.greatfire.org/blog/2014/oct/china-collecting-appl...