Why does "CORS exposes sensitive response headers" appear in ExposureGrid?

Scanners observe externally visible signals. A finding means our rules matched - validate severity and applicability in your environment.

Could this be a false positive?

Yes, depending on context and coverage limits. Especially for heuristic, partial, or pattern-based checks, corroborate with manual review.

What should I do after changing configuration?

Re-run a scan to confirm the external signal changed, then enable monitoring where your plan supports it.

CORS exposes sensitive response headers

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CORS exposes sensitive response headers: what it means, why it may matter, and how to remediate with external verification using ExposureGrid.

The problem

CORS exposes sensitive response headers: CORS headers decide which web origins may read responses in a browser. Misconfigurations can widen who can access browser-visible data.

Why it matters

Risk depends on whether responses contain sensitive data and whether cookies or credentials are involved. Some issues are high-signal; others need app-specific review.

How to check

Test with controlled cross-origin requests and review ACAO/ACAC/Vary headers on API and page routes. Re-run ExposureGrid after policy changes.

How to fix

Prefer explicit origin allowlists. Never combine Access-Control-Allow-Credentials: true with wildcard ACAO. Add Vary: Origin when ACAO varies by requester. Minimize exposed headers and allowed methods.

Identify owners for the affected component (app, edge, DNS, or mail).
Make a minimal change and validate in staging or a canary route.
Deploy with monitoring and rollback readiness.
Re-run ExposureGrid to confirm the external signal improved.

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What ExposureGrid checks

ExposureGrid probes multiple origins and routes to surface patterns like reflection, wildcards, and missing Vary where dynamic ACAO is used.

FAQ

Why does "CORS exposes sensitive response headers" appear in ExposureGrid?: Scanners observe externally visible signals. A finding means our rules matched - validate severity and applicability in your environment.
Could this be a false positive?: Yes, depending on context and coverage limits. Especially for heuristic, partial, or pattern-based checks, corroborate with manual review.
What should I do after changing configuration?: Re-run a scan to confirm the external signal changed, then enable monitoring where your plan supports it.

ExposureGrid continuously monitors these issues and alerts you before they become exploitable.

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