The 2010 runtime relies heavily on deployment technology and Code Access Security (CAS). CAS has been deprecated in newer .NET Frameworks (4.0+), though it is still supported for legacy scenarios. Organizations relying strictly on the 2010 runtime may face security audit challenges as they migrate to .NET Core or .NET 5/6/7+, which do not support the legacy VSTO architecture.
Assemblies used by solutions targeting the .NET Framework 3.5. microsoft visual studio 2010 tools for office runtime -x64-
You can download the latest redistributable package from the Microsoft Download Center Common Fixes: The 2010 runtime relies heavily on deployment technology