Roll Out Content Security Policy in Report-Only Mode Before Blocking Production Scripts

Example: a campaign embed is blocked

Trace the embed's documented resource requirements and decide whether the feature belongs on the site. Do not respond by allowing every source or disabling the entire policy. Test the narrow supported change on staging before an enforcing rollout.

Verify the complete application

Exercise login, forms, publishing, navigation and the embedded features the site intentionally supports. Monitor after enforcement and keep a rollback plan. CSP is one defensive boundary; it does not replace authorization, safe output handling or other controls against application vulnerabilities.

Should a CSP report be treated as a trusted URL to fetch?

No. Reports and resource URLs are untrusted input. Design the reporting endpoint with appropriate validation, resource limits and data handling. A security-monitoring feature should not become an unrestricted fetch service or an uncontrolled store of sensitive page information.

Primary reference and editorial note

Primary reference: developer.mozilla.org

Prepared October 19, 2026 with AI-assisted drafting and source review. Scenarios are illustrative; this guide does not claim hands-on product testing or measured results. Platform behavior can change; consult the linked current documentation before implementing changes.