Query a QNAP for any available updates using the API (PowerShell 5)

QueryQNAPUpdate.ps1

# Ignore self-certs
if (-not ([System.Management.Automation.PSTypeName]'ServerCertificateValidationCallback').Type)
{
$certCallback = @"
    using System;
    using System.Net;
    using System.Net.Security;
    using System.Security.Cryptography.X509Certificates;
    public class ServerCertificateValidationCallback
    {
        public static void Ignore()
        {
            if(ServicePointManager.ServerCertificateValidationCallback ==null)
            {
                ServicePointManager.ServerCertificateValidationCallback += 
                    delegate
                    (
                        Object obj, 
                        X509Certificate certificate, 
                        X509Chain chain, 
                        SslPolicyErrors errors
                    )
                    {
                        return true;
                    };
            }
        }
    }
"@
    Add-Type $certCallback
 }
[ServerCertificateValidationCallback]::Ignore()

# Ported/tweaked from: https://github.com/colinodell/python-qnapstats
Class QNAPStats{
    [string]$Hostname
    [string]$Username
    hidden [string]$Password
    [int]$Port

    hidden [string]$BaseUrl
    hidden [string]$SID

    QNAPStats([string]$hostname, [int]$port, [string]$username, [string]$password){
        $this.Username = $username
        $this.Password = [Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes($password))

        If(!($hostname.StartsWith('http://') -Or $hostname.StartsWith('https://'))){
            $this.Hostname = 'https://' + $hostname
        }
        Else { $this.Hostname = $hostname }

        $this.BaseUrl = [string]::Format("{0}:{1}/cgi-bin/", $this.Hostname, $port)
    }

    _InitSession(){
        If(-Not $this.SID.Length){
            $this.Login()
        }
    }

    [System.Xml.XmlElement] _HandleResponse($request){
        $data = [Xml]$request.Content

        If($data.QDocRoot.authPassed.InnerText -ne 1){
            Return $NULL
        }

        Return $data.QDocRoot
    }

    [System.Xml.XmlElement] _ExecuteGet([string]$url, [bool]$appendSid = $True){
        If($appendSid){
            $url = $url + '&sid=' + $this.SID
        }

        $request = Invoke-WebRequest -Uri $url

        Return $this._HandleResponse($request)
    }

    [System.Xml.XmlElement] _ExecutePost([string]$url, $params, [bool]$appendSid = $True){
        If($appendSid){
            $url = $url + "&sid=" + $this.SID
        }

        $request = Invoke-WebRequest -Uri $url -Method POST -Body $params

        Return $this._HandleResponse($request)
    }

    [System.Xml.XmlElement] _GetUrl([string]$url){
        $this._InitSession()
        Return $this._ExecuteGet($url, $True)
    }

    [bool] Login(){
        $params = @{'user' = $this.Username; 'pwd' = $this.Password}
        $response = $this._ExecutePost($this.BaseUrl + 'authLogin.cgi', $params, $False)

        If(!$response){
            Return $False
        }

        $this.SID = $response.authSid.InnerText

        Return $True
    }

    [string] GetFirmwareUpdate(){
        $response = $this._GetUrl($this.BaseUrl + 'sys/sysRequest.cgi?subfunc=firm_update')
        Return $response.func.ownContent.newVersion.InnerText
    }

}

# Alternatively, you can use http:// and port 8080 (not recommended)
[QNAPStats] $qnap = [QNAPStats]::new('192.168.1.5', 443, 'admin', 'yourpassword')

$qnap.GetFirmwareUpdate()
# Example responses: "none", "error", or "4.3.4.0695 Build 20180830"