How I used CSP headers to automate subdomain discovery at scale — and how you can too.
Within 24 hours, my tool parsed 500+ CSP headers and revealed 100+ forgotten subdomains — including admin panels and API gateways.
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Most bug hunters rely on brute-forcing subdomains, but I found a hidden goldmine — CSP headers.
While everyone was hammering DNS servers, I was quietly collecting subdomains without sending a single packet.
And the best part? It’s all passive, ethical, and shockingly effective.
Let me show you how.
Subdomain Enumeration is Noisy and Overused
If you’ve ever done bug bounty recon, you know the struggle:
- Brute-forcing (like with
massdnsoraltdns) is slow and gets you blocked. - Certificate Transparency logs are useful but miss internal domains.
- DNS scraping is hit or miss.
But what if I told you there’s a passive, low-noise method that most hunters ignore?
CSP headers.