Coordinators of the open-source project Fedora announced that last week unauthorized access has been detected on several of their servers that are used for digital signing of the packets that are included in the operating system.
In the public announcement for the Fedora users is said that the break-in was discovered relatively fast and localized. At the moment the developers of the operating system and the admins of the servers are taking security measurements to prevent further attacks of this kind. Hackers remain unknown.