In a letter to developers that confirmed the breach, the company did not "rule out" that developers' names, mailing addresses, and email addresses could have been accessed. However, customer information is encrypted and was not affected, Apple told Macworld.
The developer site had been down for days, leading some to wonder whether a security issue was the cause.
The letter from Apple is below:
Last Thursday, an intruder attempted to secure personal information of our registered developers from our developer website. Sensitive personal information was encrypted and cannot be accessed, however, we have not been able to rule out the possibility that some developers’ names, mailing addresses, and/or email addresses may have been accessed. In the spirit of transparency, we want to inform you of the issue. We took the site down immediately on Thursday and have been working around the clock since then.
In order to prevent a security threat like this from happening again, we’re completely overhauling our developer systems, updating our server software, and rebuilding our entire database. We apologize for the significant inconvenience that our downtime has caused you and we expect to have the developer website up again soon.