According to The NextWeb, a hacker may have used a Python script posted to GitHub to hack their way into celebrities' iCloud accounts. The script, TheNextWeb reports, uses a flaw in Find My iPhone to make it easier to crack a password using "brute force" means where hackers use a piece of software to repeatedly guess a password.
This exploit reportedly disabled any "lockout" mechanism to keep hackers from brute-forcing a password. It also went around iCloud's security notification feature, TheNextWeb notes, so users apparently had no idea that their accounts were compromised.
The motivation for the attack seems to be financial in nature: BuzzFeed reports that the hacker posted the photos to 4chan "in an attempt to earn bitcoins."
TheNextWeb says that it appears that Apple has corrected the flaw, but as of this writing, Apple has yet to comment on the matter.