User Login Security
DJ Checkup will probe your site and check if there is a user login and if so is it accessible via https.
Enforcing https is important because the credentials/data being transmitted will be encrypted.
Eavsdropping
If the user login is accessible over http this leaves one wide open for having sensitive info exposed such as usernames and passwords. The attacker can passively intercept and spy the unencrypted data transmitted between the user's browser and the server over http.
Man-in-the-middle attacks
This more intrusive attack actively intercepts and potentially manipulates the communication between two parties. The attacker can alter messages, inject malicious data, or redirect traffic.
Essentially if one has a user login ensure that https is enforced. Check out this article to see how.