Most hunters scroll past a 404. I didn’t and that single dead-looking endpoint turned into a $4,000 bounty.
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I learned early that “not found” often means “not looked at.” In large systems, endpoints die, versions split, and shadow routes persist on backends or in old mobile apps. Those forgotten endpoints are low-noise, high-impact targets. This article walks you through the mindset, the techniques and real-case archetypes that turn a casual 404 into a serious payout without being noisy or reckless.
The forgotten-endpoint phenomenon
Forgotten endpoints aren’t glamorous. They’re leftovers from migrations, abandoned feature branches, mobile clients that never got updated or configuration files left in build artifacts. Typical origins:
- API versioning drift (/api/v1/ still running while /api/v3/ is live)
- Developer debug routes and admin stubs (/debug/, /admin_old/)
- Old mobile app endpoints that the frontend stopped using but the backend still serves
- Misrouted CDN or caching configurations that expose archive paths