Harden password prompt against non-secure values

scripts/deploy-ftp.ps1

@@ -51,6 +51,9 @@ function Read-PlainOrPrompt([string]$Value, [string]$Prompt, [bool]$Secure = $fa
     if ($Value) { return $Value }
     if ($Secure) {
         $secure = Read-Host -Prompt $Prompt -AsSecureString
+        if (-not ($secure -is [System.Security.SecureString])) {
+            $secure = ConvertTo-SecureString -String ([string]$secure) -AsPlainText -Force
+        }
         $ptr = [Runtime.InteropServices.Marshal]::SecureStringToBSTR($secure)
         try { return [Runtime.InteropServices.Marshal]::PtrToStringUni($ptr) }
         finally {