The Web Application Hacker’s Handbook Discovering and Exploiting Security Flaws

If you already know one valid username (for example, an account you

control), submit one login using this username and an incorrect pass-

word, and another login using a completely random username.

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Record every detail of the server’s responses to each login attempt,

including the status code, any redirects, information displayed on screen,

and any differences hidden away in the HTML page source. Use your

intercepting proxy to maintain a full history of all traffic to and from the

server.

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Attempt to discover any obvious or subtle differences in the server’s

responses to the two login attempts.

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If this fails, repeat the exercise everywhere within the application where

a username can be submitted (for example, self-registration, password