Let’s learn how to use comments to subvert the logic of more advanced SQL queries to bypass the authentication.

Comments

There are two types of comments with MySQL:

  • --
  • #
  • /**/

-- needs a space after it for the comment to work. This is why payloads often looks like -- -.

Auth Bypass

Let’s try injecting admin'-- as our username. Final query will look like:

SELECT * FROM logins WHERE username='admin'-- ' AND password = 'something';

Now the username is admin and the remainder of the query is not ignored.