IE10: Blocked content warning dialog after login

Description of problem:
When I submit valid credentials in the login page I get to the white "Pleas wait, Loading application..." screen and before loading is finished, Internet Explorer displays a warning dialog telling me that content of "about:blank" page is blocked because it is not trusted.

Can be avoided by adding "about:blank" to the "Trusted sites" security zone in Internet Options or by unchecking "Continue to prompt when website content is blocked".

Doesn't make a good impression on the first-time login but can be easily solved and I suspect it to be IE bug because "about" is standardized URI scheme http://en.wikipedia.org/wiki/About_URI_scheme.

Version-Release number of selected component (if applicable):
ER5

How reproducible:
-

Steps to Reproduce:
1. see description

Actual results:
Warning after successful login.

Expected results:
No warning without the need to make changes in Internet Options. If there is no way to prevent this it should be documented.

Additional info: