Possible Man in The Middle Attack on Authentication When Not Using HTTPS
No Encryption before transmission
The password & confirm password inside body request for regiser & login endpoint is not encrypted by the client.
CMIIW, if the connection is not on HTTPS, someone could intercept and notes down the email & password.

It response with a set-cookie
If we set this cookie to another browser / tab / device (that not we use to register or login earlier), we will be logged in as the legitimate user.
Type of vulnerabilities
I guess.... Insecure Design. CMIIW