There seems to be some problems with the SafeFrame framework in Internet Explorer 11. No errors occur, but SafeFrame content doesn't load either, leaving an empty container. For example, the Rising Star examples at safeframes.net don't work in IE11.
I managed to get the content in our SafeFrame implementation loading by modifying the isIE-check in base.js, essentially turning it into an "is IE <= 10"-check and regarding IE11 as a non-IE browser:
isIE = (win && ("ActiveXObject" in win) && win.ActiveXObject)
I can't tell whether this is all that is needed to fix the compatibility issue completely or if some of the IE-specific code should be applied to IE11 as well. But at least adding and removing event listeners is done with the standard W3C methods in IE11, while the old attachEvent() and detachEvent() functions have been deprecated: http://msdn.microsoft.com/en-us/library/ie/bg182625%28v=vs.85%29.aspx#legacyAPIs.