(An attacker could exploit that in a number of ways. Here's a simple one: create a site with a domain name that looks really similar. http://secure.trustt-guard.com or something, it doesn't matter. When a user visits, autosubmit a form to https://secure.trust-guard.com with the malicious payload; the first thing it does is hide the error message and incorrect username. The user then enters username/password and attacker reads the values and sends it back to his site.)
What's worse, I can't find any way to report this. Does anyone see a link?