Tags: web crypto windows 

Rating: 4.0

# Web - Sad_Agent - 200

![a.png](a.png)

When we visit this URL we get

![b.png](b.png)

Whenwe click on **chek** button we see a Hidden Parameter sent which is **url**

![c.png](c.png)

after decoding the value as Base64 we get

![d.png](d.png)

Looks like it's evaluating the User-Agent so we get the page as

![e.png](e.png)

So let's try to send commands to the server by encoding the payload as Base64

**ZWNobyBleGVjKCd3aG9hbWknKTs=** -> **echo exec('whoami');**

so the request becomes

![f.png](f.png)

we get the response as

![g.png](g.png))

Oh! I see this is a Windows System

let's try **ZWNobyBzeXN0ZW0oJ21vcmUgaW5kZXgucGhwJyk7Cg==** which is **echo system('more index.php');** (After trial and error)

we get this page with the flag

![h.png](h.png)

**Flag - 0xL4ugh{S@dC0d3r_M3mbe3r_1n_0xL4ugh_&_sad_W0rld}**

Original writeup (https://github.com/rootpwn/CTF-Witeups/blob/main/0xL4ugh/Web%20-%20Sad_Agent%20-%20200/Web%20-%20Sad_Agent%20-%20200.md).