Rated 5 out of 5 stars

I've checked current version (4.0), and it seems that the issues are mentioned earlier have been resolved. I don't see any unnecessary DNS lookups, and all the traffic goes via proxy if it is configured in Firefox.

Requests to Notaries stay non-encrypted, but this probably does not a pose any serious risk.

This review is for a previous version of the add-on (4.0). 

Rated 5 out of 5 stars

I've checked current version (4.0), and it seems that the issues are mentioned earlier have been resolved. I don't see any unnecessary DNS lookups, and all the traffic goes via proxy if it is configured in Firefox.

Requests to Notaries stay non-encrypted, but this probably does not a pose any serious risk.

This review is for a previous version of the add-on (4.0). 

Rated 4 out of 5 stars

A great add-on to mitigate possible MITM attacks.
However, in its current implementation (version 3.0.3) it compromises user's privacy by potentially letting an adversary know what sites the user visits.

1) DNS request leaks.
The addon performs a DNS lookup when user loads an HTTPS site or (!) switches to a tab where such site is open. Which is worse, it doesn't honor FF proxy settings and performs DNS lookup directly even if a proxy supporting DNS lookups is being used (for instance, user is browsing via Tor).

2) Requests to the Network Notaries.
The addon makes requests to the Notaries to check the certificates. These requests are sent in plain text (as HTTP GET), so any adversary who can see this traffic could know what site was visited by this particular user.

This review is for a previous version of the add-on (3.0.3).