It went out to all ProSeries users that may have an affected client.  Click the little button to see which of your clients may have issues.  They sent it out that way instead of a critical alert because they evidently wanted to avoid panic in the streets from folks that didn't have any potential issues.  To avoid that panic, they created that handy dandy e-mail that created panic in all of us who have potential issues by wondering if the e-mail was real of if it was someone evil trying to create chaos with our computers.