Well, just looking at the Bank of America example, they don't seem to use HSTS in their landing page. How widespread is HSTS? How long is the expiry period typically set for (I would guess a long time?)
Does anyone still use browser bookmarks?
Actually, just thinking about it, it might be even simpler than this. If Bank of America wanted to, couldn't they still host their redirect landing page over SSL with a valid non-Symantec certificate, and then redirect to the ie6.bankofamerica.com page which will continue to use the bad Symantec cert? If switching certs for their web infrastructure was really difficult and they didn't want to do it, they could just build a simple little front-end web server with a valid certificate to redirect people to an IE6 download page or ie6.bankofamerica.com.
Does anyone still use browser bookmarks?
Actually, just thinking about it, it might be even simpler than this. If Bank of America wanted to, couldn't they still host their redirect landing page over SSL with a valid non-Symantec certificate, and then redirect to the ie6.bankofamerica.com page which will continue to use the bad Symantec cert? If switching certs for their web infrastructure was really difficult and they didn't want to do it, they could just build a simple little front-end web server with a valid certificate to redirect people to an IE6 download page or ie6.bankofamerica.com.