It's not really a typo but an intentionally left-out X separator for
aesthetics on the sculpture that was intended to result in gibberish
when decrypted that would clue in the decryptors to reinsert a separator
and try again, except it ended up spelling something intelligible
instead of garbage so they thought they had decrypted it properly!
```[A Break for Code Breakers on a C.I.A. Mystery - New York Times](https://www.nytimes.com/2006/04/22/us/22puzzle.html?ex=1164603600&en=52cd0484e7cbb98b&ei=5070)
> For nearly 16 years, puzzle enthusiasts have labored to decipher an 865-character coded message stenciled into a sculpture on the grounds of the Central Intelligence Agency's headquarters in Langley, Va. This week, the sculptor gave them an unsettling but hopeful surprise: part of the message they thought they had deciphered years ago actually says something else.