📰 Originally published on SecurityElites — the canonical, fully-updated version of this article. 🐛 BUG BOUNTY COURSE FREE Part of the Bug Bounty Hunter Course Day 27 of 60 · 45% complete ⚠️ Legal Disclaimer: All path traversal, LFI, log poisoning, and /proc enumeration techniques covered here are strictly for authorised security testing and educational purposes. Never test any system without explicit written permission from the owner. Unauthorised access is illegal. The target was a SaaS invoice platform — mid-sized company, active bug bounty program, $5,000 Critical cap. I found a file= parameter buried in a PDF export endpoint. Six characters: ../../../ . Thirty seconds later I had /etc/passwd in my Burp Repeater response. That alone was a High. Then I pivoted to /proc/self/environ and pulled the application’s SECRET_KEY , DATABASE_URL , and an AWS access token — all sitting in the process environment, handed to me by the Linux kernel. That’s the Critical.…