If an encryption-settings definition becomes compromised such that an unauthorized individual obtains access to the encryption key, then any data encrypted with that definition is also vulnerable because it can be decrypted using that key. It is very important that the encryption-settings database be protected (for example, using file permissions or file system ACLs) to ensure that its contents remain secure.
In the event that an encryption-settings definition is compromised, stop using the definition immediately. Any data encrypted with the compromised key should be re-encrypted with a new definition or purged from the server. This can be done on one server at a time to avoid an environment-wide downtime, but it should be completed as quickly as possible on all servers that had used that definition at any point in the past in order to minimize the risk of that data becoming exposed.