If using wkhtmltopdf in production, ensure it is updated and configured with --disable-local-file-access to prevent this exact type of leak.
The wkhtmltopdf engine follows the redirect and reads the local file. The content of /etc/passwd is rendered into the PDF. pdfy htb writeup upd
If you are running this locally, you must expose your server to the internet so the HTB challenge instance can reach it. Using a Reverse Proxy or tools like Serveo is recommended over ngrok for this specific challenge to avoid browser warning screens that might break the automated PDF rendering. If using wkhtmltopdf in production, ensure it is
Since the application blocks direct file:// or localhost inputs, the standard bypass is to host a malicious script on your own server. This script will redirect the wkhtmltopdf engine to the local file you want to read. If you are running this locally, you must
As noted in the official HTB discussion , beginners often overcomplicate this by trying to get a shell, but the goal is purely a file leak.
Entering a standard URL like http://google.com confirms the functionality—the application fetches the page and returns a PDF version of it.
Official PDFy Discussion - Page 2 - Challenges - Hack The Box