export_creds_as_system.ps1

# from https://blog.ordix.de/execute-powershell-scripts-as-system-eng
# request and store encrypted credentials for use when running scheduled tasks as SYSTEM under C:\Windows\system32\config\systemprofile\AppData\Local

Set-Content -Path "$env:temp\ExportCredential.ps1" -Value '[CmdletBinding()]
Param(
    [Parameter(Position = 0, Mandatory = $true)][string]$UserName,
    [Parameter(Position = 1, Mandatory = $true)][string]$Password,
    [Parameter(Position = 2, Mandatory = $false)][string]$Path = "$env:LOCALAPPDATA\Credential.xml"
)
$secureString = ConvertTo-SecureString -String $Password -AsPlainText -Force
$credential = [PSCredential]::new($UserName, $secureString)
$credential | Export-Clixml -Path $Path
'
$scriptFile = "$env:temp\ExportCredential.ps1"
$credential = Get-Credential -Message 'Enter credential to be exported as SYSTEM'
$password = $credential.GetNetworkCredential().Password
$actionArgument = "-File $scriptFile -UserName $($credential.UserName) -Password $password"
$action = New-ScheduledTaskAction -Execute powershell -Argument $actionArgument
$principal = New-ScheduledTaskPrincipal -UserId SYSTEM
$task = New-ScheduledTask -Action $action -Principal $principal
$regTask = $task | Register-ScheduledTask ExportCredential
$regTask | Start-ScheduledTask
$regTask | Unregister-ScheduledTask -Confirm:$false
Remove-Item -Path "$env:temp\ExportCredential.ps1"