HaveIBeenPwned.ps1

function Test-PasswordLeaked {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory, Position = 0, ValueFromPipeline)]
        [PSCredential]
        $Credential
    )
    begin {
        $SHA1 = [System.Security.Cryptography.SHA1Managed]::new()
    }
    process {
        $Hash = $SHA1.ComputeHash(
            [System.Text.Encoding]::UTF8.GetBytes($Credential.GetNetworkCredential().Password)
        )

        [GC]::Collect()

        $HashString = -join $Hash.ForEach{ $_.ToString("x2") }
        $QueryPortion = $HashString.Substring(0, 5)

        $Results = (Invoke-RestMethod -Uri "https://api.pwnedpasswords.com/range/$QueryPortion") -split '\r?\n'
        $Match = @($Results) -match $HashString.Substring(5)
        
        if ($Match) {
            foreach ($Item in $Match) {
                [PSCustomObject]@{
                    Hash     = $Item -replace '\:.+$'
                    PwnCount = [int]($Item -replace '^.+\:')
                }
            }
        }
        else {
            [PSCustomObject]@{
                Hash     = $HashString
                PwnCount = 0
            }
        }
    }
}