I think this issue is already tracked here: https://issues.openmrs.org/browse/RA-825
<meta name="referrer" content="no-referrer" />
Redirecting to /openmrs, click <a href="/openmrs/login.htm">here</a> if not redirected within 5 seconds...
It seems like older versions of LoginPageController choke on HTTP requests with a
referrer header that points to a location outside of the OpenMRS site. The above code “fixes” the issue by voiding the
referrer header then redirecting to the OpenMRS site.
For what it’s worth, I wasn’t able to reproduce this on demo.openmrs.org, so maybe it got fixed without the issue being closed?