The phone was unlocked by an unnamed third party last month (possibly Cellebrite) after being at the center of a battle between Apple and FBI.
Initially, it was believed that the FBI had taken help of an Israeli company called Cellebrite, but a report from yesterday claimed that the law enforcement agency had instead taken help from “professional hackers†to get the job done. With the phone cracked open, the FBI eventually dropped the case against Apple in the court.
The FBI has not yet reported the method to Apple via which the hackers managed to open the shooter’s locked iPhone 5c. There are also contradictory reports on whether the same method will work on other iPhones or not. Apple has also decided that it will not be suing the FBI to find out the method through which Farook’s iPhone 5c was unlocked.
[Source]