You found a PDF generator that fetches URLs. The developer blocked localhost and 127.0.0.1. Game over? Not even close. Learn the art of representing the same IP address in a dozen ways – and watch the firewall crumble.
Welcome back to the Bug Bounty Bootcamp. You’ve learned the basics of SSRF: confirm server-side requests with an external monitor, then probe localhost and internal networks. But what happens when the application knows about SSRF and blocks obvious addresses like 127.0.0.1 and localhost? That’s when the real fun begins. This lesson focuses on two advanced SSRF scenarios: PDF/screenshot generation services (where input is a URL that gets rendered into a document) and bypassing common localhost blacklists using alternative representations, custom domains, and clever services.
The Hidden SSRF Goldmine: PDF, Screenshot, and Media Generation
Any feature that takes a URL and produces a server-side artifact — PDF, screenshot, video thumbnail, image — is a prime SSRF candidate. The course highlights:
- PDF generators: “Convert this webpage to PDF” tools.
- Screenshot services: “Capture a preview of this site” widgets.