![]() Some web apps validate the CSRF tokens when they are present, but when not present, it doesn’t even bother to look for them (inconsiderate much?). In step 1, we will omit the CSRF token and see if the request goes through. Who could have expected the first step to be this simple? Well, certain web applications implement the simplest and laziest validation mechanisms, and bypassing them is a piece of cake. ![]() (To be precise, we will exploit the validation mechanism for CSRF tokens) HTTP request with CSRF token STEPWISE GUIDE TO EXPLOIT CSRF TOKENS A predictable request parameter (which was the email parameter on Jack’s website, look at the request above)īy adding a CSRF token we make the request parameter strongly unpredictable and even if there is a cookie-based session handling, there is an entire framework deployed for the CSRF protection.The server validates the CSRF token and based on that decides whether to abort or process the request.Īs stated in the previous blog, two conditions are important for a CSRF attack to execute successfully: POST /account/update-email HTTP/1.1 HOST: Cookie: session=sessioncookie123. It is then added to the subsequent HTTP requests issued by the client to the server. ![]() On the first interaction between server and client, the CSRF token is sent to the client in a very secure manner. ![]() But first, let’s dive into some important concepts, shall we? WHY CSRF TOKENS?Ī CSRF token is a secret, unpredictable value that is generated on the server side. ![]()
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