Add base-uri to the Content-Security-Policy on Cloudflare
Why it matters
An injected base tag can make every relative script URL on the page load from an attacker's server. base-uri 'self' (or 'none') stops that and almost never breaks anything.
The fix
- Open Rules, Overview, edit the Response Header Transform Rule that sets Content-Security-Policy and append ; base-uri 'self' to its value. If the origin sets the policy, change it there.
Related
- Reported by the Content-Security-Policy check
- Add a Content-Security-Policy
- Enforce the report-only Content-Security-Policy
- Send the Content-Security-Policy as an HTTP header
- Restrict where scripts can load from
- Replace 'unsafe-inline' scripts with nonces or hashes
- Remove 'unsafe-eval' from script-src
- Remove wildcard sources from script-src
- Set object-src to 'none'
- Reduce reliance on inline styles
- Fix the Content-Security-Policy syntax
Scan your domain to see whether this applies to you.