OWASP top 10 vulnerabilities CTF lesson – Poor Data Validation

CTF365 lesson is based upon OWASP top 10 vulnerabilities which is still valid in 2020. The following are the lessons that are provided by CTF365. Let me tell you they are not only top 10, instead the list is of top 11 and please note they are not in any order. You can signup security shepherd using CTF365 account and start learning.

1. Broken Session Management
2. Cross Site Request Forgery (CSRF)
3. Cross Site Scripting (XSS)
4. Failure to Restrict URL Access
5. Insecure Cryptographic Storage
6. Insecure Direct Object References
7. Poor Data Validation
8. Security Misconfiguration
9. SQL Injection (SQLi)
10. Untrusted Input
11. Unvalidated Redirects and Forwards

7. Poor Data Validation

The short description has been given in the page itself but if you want to read more about it then you can always checkout the official OWASP page where they have described it more. Please click here to go to the link.

The task here is as follows

To get the result key to this lesson, you must bypass the validation in the following function and submit a negative number.

First we check what will happen if we directly try to input a negative number.

We got the error. So direct input of negative number is not working. Lets send it to burp and see if it makes any difference.

and here is the response

Looks like there was validation only in browser. After sending the data (a negative number) we got the key. Paste the key and finish the Poor Data Validation lesson.

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