Web_Hacking/Captcha Bypass.md
2023-11-16 09:33:38 +03:30

1.8 KiB

Captcha Bypass

  • Do not send the parameter related to the captcha
    • Change from POST to GET or other HTTP Verbs
    • Change to JSON or from JSON
  • Send the captcha parameter empty
  • Check if the value of the captcha is in the source code of the page
  • Check if the value is inside a cookie
  • Try to use an old captcha value
  • Check if you can use the same captcha value several times with the same or different sessionID
  • If the captcha consists on a mathematical operation try to automate the calculation
  • If the captcha consists of read characters from an image, check manually or with code how many images are being used and if only a few images are being used, detect them by MD5
  • Use an OCR (https://github.com/tesseract-ocr/tesseract)

Online Services to bypass captchas

  • Capsolver automatic captcha solver offers the most affordable and quick captcha-solving solution. You may rapidly combine it with your program using its simple integration option to achieve the best results in a matter of seconds.

  • AZcaptcha is an automated online captcha solver API service which is highly accurate and superbly cheap OCR captcha solver solution.

A secure Captcha should have the following features:

  • It cannot be read using automatic Captcha Solver tools
  • It has the necessary high entropy content and cannot be guessed
  • Expiration on both the server and the client side with every wrong entry
  • After each user request, whether successful or unsuccessful, the captcha must be changed and the user should not be allowed to send the request again with the previous captcha.
  • Expires after a short time (about 2 minutes).
  • After successful login, Captcha will expire
  • When a new Captcha code is created, the previous code will expire
  • Using the 2FA or MFA mechanism