[the_duke]

Doesn't seem to be true, going by the Reddit discussion.

Potentially, everyone that happens to share a instance with an org that has every used Pardot is affected.

[kgermino]

I have no inside knowledge but I’m a contract developer on the Salesforce platform so I was on a lot of the public calls today.

Every org on an instance that had an org that used Pardot (huge percentage) had a service outage today.

The security breach was limited to the actual orgs (much smaller percentage) that have actually enabled Pardot in the past.

So, many (I’d guess half) of Salesforce's customers were affected with an outrage, but a much smaller percentage also had a possible data breech.