A few days back an FLA file and some instructions were posted to compliment the previously released update software for the PSJailBreak Team's PSDowngrade product, and today the PS JailBreak downgrade files have been leaked through a nice but anonymous source on IRC. Currently work is being done towards a free public PS3 downgrader alternative to the pay version, and based on a preliminary examination of the leaked PS Downgrader 3.41 PUP and Lv2diag.self files they appear to include a modified PUP along with the official Sony PlayStation 3 JIG Files that were also leaked nearly two years ago.
Usually JIG files use a special PUP to downgrade as inside its CORE_OS package is flagged for downgrading, however, this is not the case. It seems that the PUP has been modified to allow downgrading, perhaps via another yet undisclosed exploit... Time will tell for sure!
There should be a free version of the PS3 downgrade available soon. The article seems to hint at the existence of a new exploit allowing players to downgrade their console no matter the firmware version and model.