VULNERABILITY DETAILS
I have id called "swanand.mehta94@gmail.com" 
if i choose to login with valid password it will let me through 
however if i change Id to "swanandmehta94@gmail.com" (Missing ".") and logged in with valid password it will still let me through

In outcome swanand.mehta94@gmail.com and swanandmehta94@gmail.com are two different Id yet they are considered to be the same 

VERSION
Chrome Version: [ 67.0.3396.99 (64-bit)] + [stable]
Operating System: [Windows 8.1, version, and service pack level]

REPRODUCTION CASE
1. Create account something like "XXXXX.YYYY@gmail.com"
2. Try to login using valid password with login id "XXXXX.YYYY@gmail.com"
3. Logout
4. Try to login using valid password with login id "XXXXXYYYY@gmail.com" (Without dot)

FOR CRASHES, PLEASE INCLUDE THE FOLLOWING ADDITIONAL INFORMATION
Type of crash: -
Crash State: -
Client ID (if relevant): -