Swift : Privacy violation (Unmanaged memory usage)

The contents of the String object can not be deleted from memory by the software. Sensitive data leak is possible.

If sensitive data (passwords, credit card numbers, etc.) is not deleted from memory immediately after use, leak is possible. String objects are immutable; their values can only be removed by the garbage collector. The garbage collector does not run until the virtual machine runs out of memory. Memory dump created in the case of process emergency stop may contain confidential information.