The first post was edited on 18 April
After a few days of searching, I'm sure this challenge could not be true.

The challenge began in April:
https://github.com/phrutis/wif500

Before that, on February 15, the case was raised here:
https://github.com/phrutis/Fialka/issues/21

And this case on January 29:
https://bitcoin.stackexchange.com/questions/112131/bitcoin-base-58-wif-format-private-key-recovery-front-5-character-are-missing

It's quite clear that there is a contradiction between these cases.