White hat hackers announced at a conference that they had successfully hacked VeriSign SSL certificates.
This was VeriSign's same day response.
There should be an award for the clearest communication of this type, and I hereby nominate this for #1.
(Note that BS responses do not qualify. Any vendor who can't clearly state how the problem was/is being fixed, and instead just spews platitudes like, "Anyone publish this, we'll sue their sorry asses," is disqualified.)