RunWorkflow: System.InvalidOperationException: This feature has been temporarily disabled.

Unable to publish or run workflows with Task based actions (Assign Flexi task, Assign to-do task, Request approval, Request data, Request review) after installing the July 2021 CU for SharePoint 2013, 2016, 2019. Also, if you try to start a workflow on SharePoint list item, you get an error like this;

RunWorkflow: System.InvalidOperationException: This feature has been temporarily disabled. at Microsoft.SharePoint.Workflow.SPNoCodeXomlCompiler.

If these descriptions identifies error you get, then you can fix this quickly. You shoul add below lines to all of your web applications web.config file.

<authorizedType Assembly="mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" Namespace="System" TypeName="Int64" Authorized="True" />

<authorizedType Assembly="mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" Namespace="System" TypeName="Int64" Authorized="True" />

These need to be added in the authorizedTypes config section (configuration -> System.Workflow.ComponentModel.WorkflowCompiler -> authorizedTypes -> targetFx)

After you install the following July security updates for SharePoint Server, existing Microsoft SharePoint 2010 workflows stop functioning. This issue occurs because an additional validation was added in the July security update for SharePoint Server. The validation causes the existing SharePoint 2010 workflows to stop functioning.

In PowerShell, run the following cmdlets:

Add-PSSnapin Microsoft.SharePoint.PowerShell
$farm=Get-SPFarm
$farm.EnablePreParseSecurityCheckForWorkflow = $false
$farm.update()