Some customers have reported that their Managed browser hosting controls (.NET 2.0 winforms controls embedded in a user control for IE) suddenly stopped working.
Further investigation found that this occurred after applying certain security patches related to .NET 4.5 (such as those in MS KB 2858725)
In their page on Application Compatibility in .NET 4.5, Microsoft explicitly states the following under "Web Applications":
Feature: Managed browser hosting controls from the .NET Framework 1.1 and 2.0
Change: Hosting these controls is blocked in Internet Explorer.
Impact: Internet Explorer will fail to launch an application that uses managed browser hosting controls.
The previous behavior can be restored by setting the EnableIEHosting value of the registry subkey HKLM/SOFTWARE/MICROSOFT/.NETFramework to 1 for x86 systems and for 32-bit processes on x64 systems, and by setting the EnableIEHosting value of the registry subkey HKLM/SOFTWARE/Wow6432Node/.NETFramework to 1 for 64-bit processes on x64 systems.
So to sum this up: MS is explicitly blocking embedded Managed Browser Hosting Controls. this is being done for security purposes. There is every possibility that a future update could remove even the ability to override this block.
Atalasoft support strongly recommends that if you're still maintaining a user control that uses our .NET 2.0 winforms components, that you immediately begin the process of replacing that functionality using our classic ASP.NET controls (WebImageViewer, WebAnnotationViewer / WebThumbnailViewer) or our new ASP.NET controls (WebDocumentViewer /WebDocumentThumbnailer).
If you were using DotTwain user control, please look into our WingScan components for web based scanning.