These can be viewed at https://bitcoinstrings.com/blk00052.txt and are mostly commented on the "Wikileaks cablegate data" section of Hidden surprises in the Bitcoin blockchain by Ken Shirriff (2014).
Soon after block 229991 uploaded the Satoshi uploader, several interesting files were added to the blockchain using the uploader, and notably some containing content that might be illegal in certain countries, as a test to see if this type of content would make the Bitcoin blockchain illegal or not:
- tx 08654f9dc9d673b3527b48ad06ab1b199ad47b61fd54033af30c2ee975c588bd block 229999 contains a leaked private key and a link to: http://threatpost.com/en_us/blogs/ami-firmware-source-codAe-private-key-leaked-040513
- tx b96af3b69b48a82c5eae3e44ebb6ef93f30d7764b1d5b40243e11b0d374ac1b7 block 230001 http://en.wikipedia.org/wiki/Illegal_prime followed presumably by one such prime
- tx 54e48e5f5c656b26c3bca14a8c95aa583d07ebe84dde3b7dd4a78f4e4186e713 block 230009 contains the Bitcoin white paper: https://bitcoin.org/bitcoin.pdf More context: https://bitcoin.stackexchange.com/questions/35959/how-is-the-whitepaper-decoded-from-the-blockchain-tx-with-1000x-m-of-n-multisi
- tx 691dd277dc0e90a462a3d652a1171686de49cf19067cd33c7df0392833fb986a block 230203 Cablegate index. The announced filename is
cablegate-201012041811.7z. As mentioned in Hidden surprises in the Bitcoin blockchain by Ken Shirriff (2014), it has an ASCII list of several other transactions, which presumably when downloaded with the Satoshi uploader can concatenated lead to the full 7z file. Also as mentioned by Ken, it is infinitely easier for the average user to just access the cables directly on WikiLeaks :-) The data is preceded by the message:
sSEXWikileaks Cablegate Backup cablegate-201012041811.7z Download the following transactions with Satoshi Nakamoto's download tool which can be found in transaction 6c53cd987119ef797d5adccd76241247988a0a5ef783572a9972e7371c5fb0cc Free speech and free enterprise! Thank you Satoshi!
- tx dde7cd8e8f073a525c16c5ee4e4a254f847b7ad6babef257231813166fbef551 block 230229 and tx 4a0088a249e9099d205fb4760c28275d4b8965ac9fd56f5ddf6771cdb0d94f38 block 230231 contain indexes of pages from The Hidden Wiki. These can be viewed at: https://bitcoinstrings.com/blk00052.txt
So basically, this was the first obviously illegal block attempt.
Furthermore, it is likely much easier to find much worse illegal content by browsing the any uncensored Onion service search engine for 5 minutes.
Ciro estimates that perhaps the uploader didn't upload child pornography, which is basically the apex of illegality of this era, because they were afraid that their identities would one day be found.