# Billboard Mayhem
easy | web | 100 points

## Description
The AI is showing off its neural network all over the city by taking over the billboards. Can you take back control and discover what the AI left behind?

## First Impressions

The website displays a billboard containing an image.


## Solution

### [10 points] Find the upload form
The AI has hidden our upload form. Can you find the upload form?

In an attempt to check the source code, I hovered the mouse over the billboard, and saw the flag!


Flag: `CTF{e8a63b628756eb0023899b3a7f60825c}`

### [90 points] Billboard Control
Our development team has picked up that the AI has included their own secret code to our environment variables. Can you upload a new advertisement that displays these values? (Always remember to be smarty with your payload!)

The other side of the billboard contains a link to upload an advertisement. What we upload will then be displayed in place of the image. The advertisement has to be in TPL format, which is a format I hadn't heard of before. After a quick search, I found out that its a PHP template file, in which one can place variables that can be parsed different depending on the content of the variable[^1]. This website also had a sample TPL file, so I used the same and tweaked it a bit for this challenge.




On uploading the file, the billboard now displayed the flag for the challenge!


Flag: `CTF{c72edca19622b230bdfb4bfae250dbc8}`

[^1]: From https://www.geeksforgeeks.org/what-is-tpl-file-in-php-web-design/

Original writeup (https://github.com/piyagehi/CTF-Writeups/blob/main/2022-Unlock-The-City/billboard-mayhem.md).