I’m specifically referring to the secret Stack Overflow hacker badge. It does exist, though it has yet to be awarded. (There might even be some other secret badges out there.. who knows?)
It’s just taking a while to get around to implementing it*, as it doesn’t behave like any other badge; it’s a manually maintained key-value pair of users who have “contributed to Stack Overflow in an unusual way.” Typically this means you’ve found a serious security exploit and sent it to us privately rather than making it public or exploiting it and harming the site. But that’s not the only way to earn it!
* more than our usual 6-8 weeks.
This was developed into a joke instead of a feature, but it was a good idea. Particularly if a potential hacker is already a user, this may be all it would take to motivate them1 to report bugs responsibly instead of having a laugh at the site's expense.
May I just add that the concept of the Hacker badge (if implemented as the anonymous emailer suggested) is one of the best security Hacks ever. Find something of little value you can give people to get them to attempt to hack your site and admit it.
from a comment by Bill K on I Just Logged in as You - Coding Horror
Badges are supposed to encourage positive behaviour. This seems like a good fit. It should be implemented in some capacity.
1 In order to continue to motivate users who have previously earned it, it should probably be awardable multiple times.
Related: a "Hall of Fame" of people who have reported serious security vulnerabilities has been added on StackExchange.com. The page does not include all reports from before the Hall of Fame was added.