On Windows, our filter plug-in requires that the Visual C++ runtime  be installed in order to function.
Clearly, in our conventional installer, we simply invoke the redistributable package provided by Microsoft in order to achieve its installation.
Is there a way to invoke an installer in this way when a package is installed using Extension Manager? Nothing jumped out at me in the documentation, but of course if I've missed something then please point me at the right document!
There is no way to run another application during extension installation. But you can write code in your extension so that user can be prompted to download and install VC runtime by clicking a link when your extension is loaded the first time.
There is a slight chicken-and-egg problem when the extension in question is a .8bf filter plugin, written in C++ (and thus needing to link the C++ runtime itself!)
Is there any problem with statically linking the C++ runtime into a .8bf filter plugin? It looks as if we may have to take this route …