Recently upgraded to v7.10.4 and for some reason whenever the preview feature is used I get a 403 - forbidden access.
Im sure its just a configuration thing as the previous installation, v7.6.8 didnt have any problems with this.
Anyone help please? 
This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/92537-403-forbidden-access-is-denied-on-any-page-being-previewed