Where to find the information for form-based authentication
Naomi Purvis avatar
Written by Naomi Purvis
Updated over a week ago

When entering a Form-based authentication it is best to visit the target login page (the page where your login form exists), as this is where most of information we need to gather can be found.

Entrypoint URL

The entrypoint URL tells the scanner where it should start all of it's crawling and scanning from. Most often this will be the root of your web application. Which in our example would be . Please note, there is not a path associated with the URL just a / on the end, which you should include if you want the full application to be scanned.

There are times when you won't want to scan from the root of the application, instead you might want to scan a subset. For example, when you have multiple applications running on the same target, but which live at different paths. For our example:




In this case, you would want to add 3 separate authentications each using one of the paths in the list.

Login Page URL

The Login Page URL is the URL at which your login form can be found. In this example our login page is at (which can be seen in the URL bar at the top of the following screenshot):

Login Request URL

This is the URL to which your application sends the data that users have entered into the form. This can be found by right-clicking on the form (such as on the username field), and then selecting Inspect:

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You are looking for the form tag which encloses the username and password fields on your login form. The form tag will have an action field and the value of that field is what you're looking for. In our example, the value is login.php, which can be seen below:

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In our example we see login.php is the value we see in the form. We need to add the prefix that we made a note of in our Login Page URL section above. So, the value we need to enter into our Login Request URL field is You may notice that this is the same as our Login Page URL from the previous section - this may not be the case in your app.

Logout URL

The easiest way to find this would be to login to the application and find the Logout button on your page (it may say Log Out or Sign Out or something similar). If you hover over the button you'll see the Logout URL in in the bottom of your page, you can also right click and 'Save link address', then paste into Intruder.

If that's not working, you can right-click on the logout button and click on Inspect:

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In our example the Logout URL is set to logout.php but it needs to be fully-qualified by adding the path to the current page in front of the page. Which you can see in the screenshot above

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Note that if you have a Logout URL that includes query parameters (e.g. http://www.example.com/login?action=logout), then we would recommend always including the Logged In Pattern (optional) parameter.

Logged In Pattern

In our example above an appropriate value for the Logged In Pattern would be Logout as it appears on every page when a user is authenticated.

Username Field

Logout of the application and go to your Login Page URL, right-click on the username field:

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You are looking for the value of the name field of the username input which in our example is username. When you mouse over the input field in the source code it should highlight the username text entry box on your screen.

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Password Field

If you're not already, go to your Login Page URL and right-click on the password field:

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You are looking for the value of the name field of the password input which in our example is password , it could be named something different in your app. When you mouse over the input field in the source code it should highlight the password text entry box on your screen. Additionally, the password field is usually always set to type="password":

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CSRF Token Field

Anti-CSRF tokens are usually found in forms which submit data to the application. But, it might be possible that your application doesn't have an anti-CSRF token at all.

Anti-CSRF tokens will usually have the following properties:

  • It will be an input field in the same form as your login fields

  • The input field will have a type and it will be set to "hidden" , which you can see in our example below as type="hidden"

  • The input will have a value and that value will usually be a long random block of text

  • The input will have a name but there is no specification which dictates what the name should be, it can be anything. But, the name may include the term csrf , authenticity , verification or token.

In our example below you can see the field that fits all these properties is the user_token field, and this is our CSRF Token Field:

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Additional Parameters

While searching your form you may find additional input fields. For example, when you view the Intruder Portal login form you will see another input field with the name commit and the value set to Log in which can be seen below:

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You need to add these fields to the Additional parameters section when adding your authentication. If you don't then your authentication may fail. So, for the Intruder Portal Login form we would need to add the following to our authentication:

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Username & Password

Both of these are mandatory. They should be the values that you have configured for your user in your application.

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