PS3 Debug Firmware 3.66 Leaked
The debug firmware of the PS3 3.66 update has been leaked on to the net, but there is no need to get all excited or angry - this does not mean the onset of custom firmware.
A hacker over at demonhades.org known as Consoledev has got their hands on the debug firmware and leaked it online, but as an associated forum member states:
No, this does not mean CFW, but this hopefully can be useful to devs in establishing the future of CFW. This firmware is only for developers, researchers and this will only work on TEST units.
So do not expect to be able to use this yourselves unless you have a test unit, but as said, this could carve the way towards future CFW (custom firmware).