Simple Membership < 4.7.8 - Unauthenticated Administrator Account Takeover via Registration Username Collision

The Simple Membership WordPress plugin before 4.7.8 does not verify whether user creation failed during registration before using the returned value as a user ID to update an account, allowing unauthenticated attackers to overwrite the primary administrator's account data (including the email address) and take over that account through the password reset flow.