Can not login to my Comcast Xfinity account

Could you please show the message, screen shot maybe. Sounds like a security issue. Did you by any chance have an auto update, and why if only a few minutes ago, it seems a bit odd you posted here Personally I would, if Windows, Clear cookies in Fx for the domain. Close Fx and do proper [Restart] of Windows. i.e. try something to resolve it as what ever you try helps to rule out underlying parameters, assuming it is not down to the website. Have you tried the site again ??