XenForo 2.3 adds a
new feature allowing public content to be embedded in any page. This update adds support for your forum to embed the publicly accessible content of any XenForo 2.3+ forum that has enabled this feature.
How to configure: go to your admin panel, go either to this add-on's options or to the XenForo entry in the BB code media sites menu, then add the hostname of the XenForo 2.3+ forum you want to embed from. Make sure that the target website runs XenForo 2.3, which at this time is a very short list.