Public/Get-MSCatalogUpdate.ps1

function Get-MSCatalogUpdate {
    <#
        .SYNOPSIS
        Query catalog.update.micrsosoft.com for available updates.

        .DESCRIPTION
        Given that there is currently no public API available for the catalog.update.micrsosoft.com site, this
        command makes HTTP requests to the site and parses the returned HTML for the required data.

        .PARAMETER Search
        Specify a string to search for.

        .PARAMETER Strict
        Force a Search paramater with multiple words to be treated as a single string.

        .PARAMETER AllPages
        By default this command returns the first page of results from catalog.update.micrsosoft.com, which is
        the latest 25 updates matching the search term. If you specify this switch the command will instead
        return all pages of results. This can result in a significant increase in the number of HTTP requests
        to the catalog.update.micrsosoft.com endpoint.

        .EXAMPLE
        Get-MSCatalogUpdate -Search "Cumulative for Windows Server, version 1903"

        .EXAMPLE
        Get-MSCatalogUpdate -Search "Cumulative for Windows Server, version 1903" -AllPages
    #>

    
    [CmdLetBinding()]
    param (
        [Parameter(
            Mandatory = $true,
            Position = 0
        )]
        [String] $Search,

        [Parameter(
            Mandatory = $false,
            Position = 1
        )]
        [Switch] $Strict,

        [Parameter(
            Mandatory = $false,
            Position = 2
        )]
        [Switch] $AllPages,

        [Parameter(DontShow)]
        [String] $Method = "Get",

        [Parameter(DontShow)]
        [String] $EventArgument,

        [Parameter(DontShow)]
        [String] $EventTarget,

        [Parameter(DontShow)]
        [String] $EventValidation,

        [Parameter(DontShow)]
        [String] $ViewState,

        [Parameter(DontShow)]
        [String] $ViewStateGenerator
    )

    if ($Method -eq "Post") {
        $ReqBody = @{
            "__EVENTARGUMENT" = $EventArgument
            "__EVENTTARGET" = $EventTarget
            "__EVENTVALIDATION" = $EventValidation
            "__VIEWSTATE" = $ViewState
            "__VIEWSTATEGENERATOR" = $ViewStateGenerator
        }
    }
    $UriSearch = [Uri]::EscapeUriString($Search)
    $Params = @{
        Uri = "https://www.catalog.update.microsoft.com/Search.aspx?q=$UriSearch"
        Method = $Method
        Body = $ReqBody
        ContentType = "application/x-www-form-urlencoded"
        UseBasicParsing = $true
    }
    $Results = Invoke-WebRequest @Params

    $HtmlDoc = [HtmlAgilityPack.HtmlDocument]::new()
    $HtmlDoc.LoadHtml($Results.RawContent.ToString())
    $NextPage = $HtmlDoc.GetElementbyId("ctl00_catalogBody_nextPage")
    $EventArgument = $HtmlDoc.GetElementbyId("__EVENTARGUMENT")[0].Attributes["value"].Value
    $EventValidation = $HtmlDoc.GetElementbyId("__EVENTVALIDATION")[0].Attributes["value"].Value
    $ViewState = $HtmlDoc.GetElementbyId("__VIEWSTATE")[0].Attributes["value"].Value
    $ViewStateGenerator = $HtmlDoc.GetElementbyId("__VIEWSTATEGENERATOR")[0].Attributes["value"].Value
    $Table = $HtmlDoc.GetElementbyId("ctl00_catalogBody_updateMatches")
    $Rows = $Table.SelectNodes("tr")

    $Output = foreach ($Row in $Rows[1..($Rows.Count - 1)]) {
        $Cells = $Row.SelectNodes("td")
        $Title = $Cells[1].innerText.Trim()
        if ($Strict) {
            if ($Title -like "*$Search*") {
                [PSCustomObject] @{
                    PSTypeName = "MSCatalogUpdate"
                    Title = $Title
                    Products = $Cells[2].innerText.Trim()
                    Classification = $Cells[3].innerText.Trim()
                    LastUpdated = (Invoke-ParseDate -DateString $Cells[4].innerText.Trim())
                    Version = $Cells[5].innerText.Trim()
                    Size = $Cells[6].SelectNodes("span")[0].InnerText
                    SizeInBytes = [Int] $Cells[6].SelectNodes("span")[1].InnerText 
                    Guid = $Cells[7].SelectNodes("input")[0].Id
                }
            }
        } else {
            [PSCustomObject] @{
                PSTypeName = "MSCatalogUpdate"
                Title = $Title
                Products = $Cells[2].innerText.Trim()
                Classification = $Cells[3].innerText.Trim()
                LastUpdated = (Invoke-ParseDate -DateString $Cells[4].innerText.Trim())
                Version = $Cells[5].innerText.Trim()
                Size = $Cells[6].SelectNodes("span")[0].InnerText
                SizeInBytes = [Int] $Cells[6].SelectNodes("span")[1].InnerText 
                Guid = $Cells[7].SelectNodes("input")[0].Id
            }
        }
    }
    $Output | Sort-Object -Property LastUpdated -Descending

    # If $NextPage is $null then there are more pages to collect.
    if ($null -eq $NextPage) {
        if ($AllPages) {
            $NextParams = @{
                Search = $Search
                AllPages = $true
                EventArgument = $EventArgument
                EventTarget = 'ctl00$catalogBody$nextPageLinkText'
                EventValidation = $EventValidation
                ViewState = $ViewState
                ViewStateGenerator = $ViewStateGenerator
                Method = "Post"
            }
            Get-MSCatalogUpdate @NextParams
        }
    }
}