Blocked a frame with origin "https://mydomain.com" from accessing a cross-origin frame

hi can someone please help.
since upgrading to .76 im seeing the following error, how do i resolve it?

2018-08-20 21:38:45 ERROR (MainThread) [frontend.js.latest.201808180] https://mydomain.com/frontend_latest/app-75bf2674.js:2:123881 Uncaught SecurityError: Blocked a frame with origin "https://mydomain.com" from accessing a cross-origin frame.

i can still access the frontend from https://mydomain.com