Quote
As best I’ve been able to ascertain, these builds were available to download by anyone, but they were obscured by long, unguessable URLs. Someone within Apple leaked the list of URLs to 9to5Mac and MacRumors. I’m nearly certain this wasn’t a mistake, but rather a deliberate malicious act by a rogue Apple employee. Whoever did this is the least popular person in Cupertino. More surprises were spoiled by this leak than any leak in Apple history.