Update: Several users who updated to PS3 Firmware 3.42 have now confirmed (along with Sony directly) that Sony has indeed added 'additional security features' and patched the PS3 exploit used for PS JailBreak, PSGroove and PSFreedom as expected so it is advised you do NOT update if you plan to use them.
For those who just signed in to PlayStation Network, PS3 Firmware update 3.42 is now available to download.
Download: PS3 Firmware 3.42 Update (US) / PS3 Firmware 3.42 Update (EU)
While we can speculate on whether Sony blocked PS JailBreak with it, etc feel free to grab it below and report in the comments any changes you notice and we will update the news accordingly.
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