So I encountered the issue where I see another app having a posting authority on my account yesterday. To read more about it, take a look at here: https://steemit.com/esteem-feedback/@gaman/how-do-i-remove-esteemapp-in-the-posting-key
After much research, I found a way to remove it. It is thru using the cli_wallet. The cli_wallet has this function:
update_account_auth_key(string account_name, authority_type type, public_key_type key, weight_type weight, bool broadcast)
This method updates the key of an authority for an exisiting account.
Warning: You can create impossible authorities using this method. The
method will fail if you create an impossible owner authority, but will
allow impossible active and posting authorities.
Parameters:
account_name: The name of the account whose authority you wish to
update (type: string)
type: The authority type. e.g. owner, active, or posting (type:
authority_type)
key: The public key to add to the authority (type: public_key_type)
weight: The weight the key should have in the authority. A weight of 0
indicates the removal of the key. (type: weight_type)
broadcast: true if you wish to broadcast the transaction. (type: bool)
So, as I understand it, you have to set the weight to 0 to remove the key.
I haven't tried this yet, as I am stuck in running the cli_wallet remotely. I am currently installing steemd in my server and once I am done with it, I will let you guys know if I am successful in removing it.