A few days back, I read an article about Google Authentication. A bug was mentioned in the article, that Google login status can be easily accessed by calling out some images. After reading the article, I got an idea that why don’t we use this bug in a positive approach to validate user authentication. This same idea has been implemented in this post to do email validation. I have used Google email login system (not OAuth) using Angular 4 CLI project. Take a look at the live demo ( Make sure to login into your Google account in another tab to do this validation).