This app was mentioned in 1 comment, with an average of 3.00 upvotes
https://www.reddit.com/r/CODZombies/comments/59hpti/want_to_help_break_the_adfgx_motd_cipher_here_is/ here is the PC version for it but the link is broken :/. edit: here is the android version https://play.google.com/store/apps/details?id=com.adfgx_cloud_solver_android.adfgx_cloud_solver_android&hl=en_GB