Block cipher challenge

Level: CTR mode

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Ciphertext (hexencoded), for easy copy-paste

8c0b883a87914c31acabab15f2c1c6bb3737c5d8532ec4bccbe158af7c92c99efeef72b36783fb0e2dc54cecea2848423791d427044091e041497dc0c1f2e48c

Ciphertext (hexencoded):

8c0b883a87914c31acabab15f2c1c6bb 3737c5d8532ec4bccbe158af7c92c99e feef72b36783fb0e2dc54cecea284842 3791d427044091e041497dc0c1f2e48c

Plaintext (hexencoded):

8c0b883a87914c31acabab15f2c1c6bb 7b22757365726e616d65223a20226775 657374222c202269735f677565737422 3a20747275657d090909090909090909

Plaintext:

\x8c\x0b\x88:\x87\x91L1\xac\xab\xab\x15\xf2\xc1\xc6\xbb {"username": "gu est", "is_guest" : true}\t\t\t\t\t\t\t\t\t

Final plaintext

{"username": "guest", "is_guest": true}