i've found article about xdna and dual mining.
if you know russian, you may waste few minutes and read it, the author thinks that hold xdna is very risky.
article link on medium
https://medium.com/@changetimes/%D0%B4%D1%83%D0%B0%D0%BB-%D0%BC%D0%B0%D0%B9%D0%BD%D0%B8%D0%BD%D0%B3-eth-keccak-9555b4904e37