After upgrading ASP .Net 3.5 app to .NET 4.5.2 we started receiving numerous “This is an invalid webresource request” errors.
We have traced the error to missing css from Obout control dll. The control is used widely and we cannot replace it.
The upgrade was performed month and half ago and we still receive the same number of errors.
I am aware of other Stackoverflow questions regarding the same problem, but some of the answers suggest problem disappears with time. This has not happened in our case yet, almost 2 months after upgrade.