The forgery was issued to the unknown attackers on 10 July by DigiNotar, a Dutch SSL certificate authority. For more than two months it would have allowed them to set up fake versions of Google websites that appeared genuine to users and their web browsers.
“This CA should receive an internet death sentence as their carelessness may have resulted in deaths in Iran,” an unknown researcher who verified the certificate wrote. “This cert was issued in JULY of 2011 and it is now just a few days before SEPTEMBER. It is being used in the wild against real people in Iran *right* now.”
...“While we investigate, we plan to block any sites whose certificates were signed by DigiNotar,” a statement issued by Google announced.
The issue is much broader than just the Google certificates. Also many government certificates in the Netherlands are signed by Diginotar. A few hours ago the ministry of Internal Affairs in the Netherlands announced that the Dutch government will stop using Diginotar as a certificate issueing body. The announcement was made by minister Piet Hein Donner himself, which is an indication that the Dutch government takes this hack very seriously.
The source of the hack and the fake certificates seems to be Iran. Besides a fake certificate for google.com, also certificates have been issued for the Yahoo and Mozilla site, and a number of blog platforms including WordPress.