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The Content Security Policy is report-only

MediumConfirmedQuick winweb.security-headers.csp-report-only

What this check looks for

A policy exists but the browser only reports what it would have blocked. Nothing is actually blocked.

Why it matters

Report-only is exactly the right way to develop a policy and is not protection. Sites often stay in this state for years, showing a policy in the headers while enforcing nothing.

When the check passes, your report says: “The Content Security Policy is enforced, not merely reported”.

What it costs your score

When this check fails it removes 8 points from your Web security score, before the status, confidence and repeat multipliers are applied. Web security carries a weight of 8 in the overall score.

It shares the web-security.csp family ceiling of 30 points: however many findings that family produces, together they cannot remove more than that from Web security. One underlying problem showing up in several places is still one problem.

Severity
medium
Default confidence
confirmed
Status when triggered
warn
Deduction
8 points
Family cap
web-security.csp · 30
Category
Web security
Module
Web security headers
Fix owned by
user
In the ruleset since
2026.09

How the whole score is calculated

How to fix it

Move the policy to the enforcing header once its reports are clean.

A report-only policy blocks nothing, however strict it looks.

  1. Review recent violation reports and fix the legitimate sources.

  2. Send the same value under Content-Security-Policy.

  3. Keep a stricter candidate under the report-only header to continue tightening safely.

How to confirm it worked

  • curl -sSI https://‹host›/ | grep -i '^content-security-policy:'

A named slot like ‹domain› — and the braces left in the configuration below — is filled in with your own values when this rule appears on a report.

Remediation by platform

nginx
add_header Content-Security-Policy "default-src 'self'; object-src 'none'" always;
Apache
<IfModule mod_headers.c>
	Header always set Content-Security-Policy "default-src 'self'; object-src 'none'"
</IfModule>
Caddy
header {
	Content-Security-Policy "default-src 'self'; object-src 'none'"
}
Cloudflare
Rules → Overview → Create rule → Response Header Transform Rule → Set static → Content-Security-Policy = default-src 'self'; object-src 'none'
(Dashboard path as at 2026-09; Cloudflare reorganised these pages and may again.)

  • The always flag matters: without it nginx omits the header on error responses, which are exactly the ones an attacker aims for. Note also that any add_header in a location block discards every add_header inherited from the server block.

  • Shown because the response identified Apache. Put it in the virtual host rather than .htaccess: .htaccess is re-read on every request, and Header always set there runs too late for responses the server generates itself.

  • A Transform Rule adds the header at Cloudflare's edge, so it applies only to responses that reach visitors through Cloudflare. An origin that is reachable directly — by IP, or through a DNS record that is not proxied — still serves the response measured here without it. Setting it at the origin covers both paths.

Technical detail

The header is Content-Security-Policy-Report-Only. Browsers evaluate it and send violation reports; they load the resources anyway. When the reports are clean, send the same value under Content-Security-Policy. Both headers can be sent at once — an enforcing baseline plus a stricter report-only candidate — which is how a policy is tightened without risk.

Standards and references

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