Headers Security
medium Severity
Free Check
Cross-Origin Resource Isolation (COOP, COEP, CORP)
Evaluates COOP (Cross-Origin-Opener-Policy) and COEP headers to isolate your browsing context from Spectre-like side-channel attacks.
Why It Matters
Cross-origin isolation prevents other browser tabs from accessing memory objects and unlocks high-resolution timers (SharedArrayBuffer).
How We Check This
We check for Cross-Origin-Opener-Policy: same-origin and Cross-Origin-Embedder-Policy: require-corp headers.
How to Fix & Implement
Copy-paste configuration blocks tailored for your web server or edge proxy.
nginx snippet
add_header Cross-Origin-Opener-Policy "same-origin" always; add_header Cross-Origin-Embedder-Policy "require-corp" always;
Frequently Asked Questions
Does COOP prevent tab-nabbing?
Yes. Setting COOP to same-origin severs window.opener references from cross-origin tabs.