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The Bug Bounty Playbook: Authentication Bypass
The Bug Bounty Playbook · Part 3 of 20. 317 disclosed HackerOne reports analysed across 20 programs. Five recurring patterns. One testing framework you can run on every authentication endpoint.
30-second version
Authentication bypass is never about breaking the password. Across 317 top disclosed HackerOne reports, five patterns repeat: cookie scope theft via subdomain takeover, OTP and 2FA logic flaws, SSO and SAML protocol confusion, client-side response manipulation, and exposed infrastructure with missing auth. Every single one finds something the server trusts instead of the password and exploits that trust. The password was never the point.
The most upvoted auth bypass on HackerOne earned $20,160 by reading cached plaintext passwords from a Pulse Secure VPN. The second most upvoted earned $0 by changing one parameter in a Snapchat logout request. The third most upvoted earned $0 by claiming an expired Roblox subdomain and stealing session cookies.
Three completely different techniques. Three completely different impact levels. One common thread: none of them touched the password.
I analysed 317 disclosed authentication bypass reports from HackerOne to understand why. I ranked them by community upvotes and bounty, read the top 35 in full detail across 20…
