Google Leaks Your Alternate Email Addresses to Unauthenticated Users
The Google Login Flow leaks additional email account information to unauthenticated users. I discovered this in the Google Account Login flow while building KoiPhish.
Responsible Disclosure I reported this issue to Google and they looked into it and after a about 5 weeks of back and forth they decided that this is not an issue worth fixing. After asking if I can post about it publicly I got Google’s okay.