Captcha bypass

1- Proof of Concept

1. Create a new request by entering right captcha value.

2. Intercept the request in a proxy tool.

3. The request will look like this:

4. Now change the method from POST to PUT and right submit the request.

5. The request will look like:

6. Repeat the request for any number of times and observe that every time instead of checking for a new captcha value, the old value or ANY VALUE from captcha is accepted.

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2- Proof of Concept

1. https://www.coinbase.com/signup

2. Fill the input field and Validate the captcha.

3. Trun on Brurp submit form and capture the request.

4. Remove the g-recaptcha-response( response value) and foreword it.

Impact:

Fake accounts can be created. Also username enumeration can be performed because no application will allow two email to choose same email.

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3- Proof of Concept

1. https://www.website.com/login

2. Fill the input field and Validate the captcha.

3. Trun on Brurp submit form and capture the request.

4. Remove the recaptcha-response( response value with Header) and foreword it.

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