We were not able to reproduce this issue on any of our machines during pre-release testing for v4.28. Then after some R&D, we are able to reproduce this issue.
Cause of the problem: if value of "HKEY_CLASSES_ROOT\.js\Content Type" is set to "text/plain" then issue is reproducible. In any javascript file, the content type should be “text/javascript” in the response header but in the above registry setting it is "text/plain", so the browser won't allow it.
Solution: Open theregistry and changed the value of "HKEY_CLASSES_ROOT\.js\Content Type" to "text/javascript".
Please let us know the above solution works for you all.