Thanks for posting! Since the encryption is a one-way hash, it really is not possible to decrypt it within the Adtran. You will need to overwrite and/or shut off the feature. To overwrite, you will just need to enter your password commands again with the password you choose. To turn off the feature, you will need to enter "no service password-encryption" and then reenter each password. Below is an example.
TA900(config)#no service password-encryption
TA900(config)#enable password adtran
TA900(config)#username admin password adtran
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