Happened to me a couple months ago (with Amazon.com). I was on a Time Warner Cable connection (not mine) and their DNS servers had been compromised and routing folks to the a fake login page that was 'statically perfect' of the current login page.
At least you received a warning.
I was attempting to log in, unsuccessfully, a few times, and then figured something must be up since it would just refresh to the home page/login page again, although logging in via my iPad (cellular) worked fine. I then checked the page connection, which was not pointing to Amazon's true site, and then the source code of the page also hinted to several themes and non-Amazon references.
I immediately used another (ISP) connection to log in and changed my password, and then contacted TWC to speak with their security folks for a while - needless to say, they were happy to have received the information and were looking into it - actually, were on it quick and I was actually impressed with the response and action they took while I was on the phone with them. I went ahead and then changed that home's DNS servers to point to Google - just anything else than what they were using.
Edited 1 time(s). Last edit at 09/08/2015 08:04AM by onthedownlow.