Locking withdrawals to predefined addresses or disabling withdrawals for currencies is a good security improvement in itself, but it will only be a true security improvement if you lock all addresses for all currencies.
In this case, an account's credentials were to be compromised and if only some currencies have locked addresses while leaving others unlocked, an attacker would still be able to withdraw funds to an address under his control for one of the currencies not set to a locked address. The attacker could simply exchange the funds in the account to a currency not set to a locked address and withdraw.
If you wish to increase the level of security of your account by locking addresses, this will only help if all addresses are locked. We strongly suggest that you will review the locked withdrawal address settings on your account.
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