Fixes the missing authorizedType issue after July 2026 CU

Fix-SystemCodeDom.ps1

<#
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  SUMMARY: 
    
   This script adds the missing authorizedType entry prevening SP2010 workflows from working after installing July 2026 CU
   
   Reference: 
   https://blog.stefan-gossner.com/2026/07/17/trending-issue-sharepoint-2010-workflows-are-failing-after-installing-july-2026-cu/
   Version History:
    1.0 - initial version
  
#>


param(
    [Parameter(Mandatory = $true)]
    [string]$WebApplicationUrl
)

$webApp = Get-SPWebApplication $WebApplicationUrl

if ($null -eq $webApp)
{
    throw "Web Application '$WebApplicationUrl' not found."
}

$modification = New-Object Microsoft.SharePoint.Administration.SPWebConfigModification

$modification.Owner = "CustomWorkflowAuthorizedType"

$modification.Path = "configuration/System.Workflow.ComponentModel.WorkflowCompiler/authorizedTypes/targetFx[@version='v4.0']"

$modification.Name = "authorizedType[@Assembly='System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' and @Namespace='System.CodeDom' and @TypeName='*' and @Authorized='True']"

$modification.Sequence = 0
$modification.Type = [Microsoft.SharePoint.Administration.SPWebConfigModification+SPWebConfigModificationType]::EnsureChildNode

$modification.Value = '<authorizedType Assembly="System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" Namespace="System.CodeDom" TypeName="*" Authorized="True" />'

# Prevent duplicates
$existing = $webApp.WebConfigModifications |
    Where-Object {
        $_.Owner -eq $modification.Owner -and
        $_.Path -eq $modification.Path -and
        $_.Name -eq $modification.Name
    }

if ($existing)
{
    Write-Host "Modification already exists." -ForegroundColor Yellow
}
else
{
    $webApp.WebConfigModifications.Add($modification)
    $webApp.Update()

    Write-Host "Applying web.config modifications..." -ForegroundColor Green
    $webApp.Parent.ApplyWebConfigModifications()

    Write-Host "Modification added successfully." -ForegroundColor Green
}