Users in our enterprise (2,000+ clients) have to manually allow an MCB exception when using an in-house application every time we use it. I have exported the registry, made the change to mixed content blocking active content in about:config, and then re-exported the registry and have been unable to find any changes in the registry. Therefore, I am out of ideas as to how to deploy a package from Configuration Manager (Microsoft's enterprise client management) to disable this feature so people can work unhindered by Firefox.

Currently we are getting around this by telling our users to NOT use Firefox. This will be a make or break for this browser in our environment.