Security
Security header rollout: add browser protections without breaking the site
Security header rollout should begin with the browser behavior each header controls and the application compatibility risk. CSP, HSTS, frame restrictions, MIME sniffing, referrer policy, and permissions policy are not interchangeable checkboxes; some can block production functionality if deployed without observation.
Inventory current headers and application features
Capture responses for representative HTML, API, download, error, and authenticated routes. Identify frames, external scripts/styles/fonts, workers, media, forms, redirects, and cross-origin integrations that a new policy may affect.
Do not assume one header set fits both the storefront and a third-party application/client area.
Deploy high-impact policies in stages
CSP is well suited to Report-Only during discovery; HSTS should begin only after HTTPS is stable; frame-ancestors/X-Frame-Options need known embedding requirements. Other headers can often enforce immediately after compatibility review.
Keep a rollback path and source-controlled configuration.
Test real interactions, not just scanners
Automated scanners confirm syntax/presence but may not click checkout, submit forms, load consented analytics, open modals, run tools, or exercise third-party integrations. Browser tests should cover critical workflows with console/CSP violation monitoring.
Test both desktop and mobile where site behavior differs.
Make headers part of regression CI
Assert required directives, no unexpected report-only drift, no unsafe wildcard additions, and live browser behavior. Security headers are operational configuration and should receive the same change control as application code.
- Map features before policies.
- Stage CSP/HSTS carefully.
- Browser-test interactions.
- Regression-test headers in CI.