The Simple Membership WordPress plugin before 4.8.3 does not avoid transmitting a newly registered member's plaintext password in a URL query string when an optional auto-login-after-registration feature is enabled, exposing the credential in browser history and in web server, proxy, and CDN access logs to anyone able to read them.
https://wpscan.com/vulnerability/7d9a6fe5-fcfc-48f0-a811-8623a69422df/