You might have missed this one, if you believed those hashes returned to you by the Sony servers, like I initially did.
Sony servers still list the known 6e070… one if you check the servers: http://pastie.org/private/gabi30ry5grctrxatb0c8w but the file you get when you download it, is actually:
MD5:2A52196399A4B96EA568AAFA65D1A27E
CRC32:894AB144 / CRC16:C05A
SHA1:C372CE26267590DC851EEC66B73A162A8CAC76EA
HMAC_SHA1:0xCD4BA19DE5A0A1F95D32379AE24594595070076A
There is no known official changelog, but because the previous release of firmware 3.56 was plagued by an old harddisk bug (which rendered your console useless if you exchanged the harddisk after installing firmware 3.56) there is little headroom for speculation what is changed in this version.
Same warnings as last time apply:
do not update if you want homebrew or modified firmware
Already added to the PS3 System Software (aka Firmware) versions page.
thanks Guest_4268 for heads-up 
Update:
Checked the harddisk bug out and apparently this fix works as long as you didn’t reformat the old drive. Just insert the old drive with the bugged 3.56-1st installed on it and reinstall this 2nd release, after that you can exchange the harddisk and reinstall the 2nd release again.
If you by any change reformatted the (old) drive you are out of luck (and maybe a 3.56-3rd release might fix the issue). To be continued so it seems…
Now about those random numbers, it would be interesting to see if they used a different one for this 2nd release 
(if they didn’t, this might reveal those private keys you need for signing)
Note: 3.56 SHOP was silently replaced too (as expected after the above mentioned CEX/Retail rerelease).
MD5:BFCFE6E3E1A151817651928F736997F9
CRC32:5AEF9EC2 / CRC16:D0F5
SHA1:20B5695A532F483A10A0990E7FC76B07226E85DC
HMAC_SHA1:0x0BE9862C87DEC6508E67EC0A870C39D61A389AE6
