Server: Mastodon

Announces web server software and optionally version details.

X-Frame-Options: DENY

Instructs the browser if the current website can be embedded in HTML frame by another website. Since this allows the parent website to control the framed page, this creates a potential for data theft attacks ("clickjacking") and most sensitive websites won't allow them to be framed at all (deny) or just allow parts of them to be embedded in frames created by themselves only (samesite).

X-Content-Type-Options: nosniff

A non-standard but widely accepted header introduced originally by Microsoft to disable "content sniffing" or heuristic content type discovery in absence or mismatch of a proper HTTP Content-Type declaration, which led to a number of web attacks. In general, presence of the header with its only defined value of nosniff is considered as part of a properly secured HTTP response.

X-XSS-Protection: 1; mode=block

Controls an Cross-Site Scripting (XSS) filters built into the majority of web browsers. The filter is usually turned on by default anyway, but requirement to set the header to 1 became part of canonical set of "secure" HTTP headers. Over time, vulnerabilities in the "sanitizing" mode filter were found, so 1; mode=block became the recommended value. Some companies decided that they don't really need a browser-side XSS filter to mess with their web services which are XSS-free anyway and they became consciously disabling the XSS filter by setting the header to 0.

Strict-Transport-Security: max-age=31536000

HTTP Strict Transport Security (HSTS) is an opt-in security enhancement that is specified by a web application through the use of a special response header.

base-uri 'none'; default-src 'none'; frame-ancestors 'none'; font-src 'self' https://static-cdn.mastodon.social; img-src 'self' https: data: blob: https://static-cdn.mastodon.social; style-src 'self' 'unsafe-inline' https://static-cdn.mastodon.social; media-src 'self' https: data: https://static-cdn.mastodon.social; frame-src 'self' https:; manifest-src 'self' https://static-cdn.mastodon.social; connect-src 'self' data: blob: https://static-cdn.mastodon.social https://files.mastodon.social wss://mastodon.social; script-src 'self' https://static-cdn.mastodon.social; child-src 'self' blob: https://static-cdn.mastodon.social; worker-src 'self' blob: https://static-cdn.mastodon.social

• Policy delivery method: Content-Security-Policy
• Enforcement: True

• Consider adding block-all-mixed-content directive if your website is only accessible over TLS and you are certain it doesn not have any legacy plaintext resources. Otherwise you may add adding upgrade-insecure-requests directive if your website may still have some legacy plaintext HTTP resources and you want them to be still available rather than blocked

• Policy that has script-src but not object-src (or default-src: 'none' allows script execution by injecting plugin resources. Please read our CSP guidance for more details for more details

• Origin style-src 'unsafe-inline' allows bypassing of CSP and execution of inlined untrusted scripts. Use 'nonce-' or 'sha256-' instead

• You should definitely try using 'strict-dynamic' to eliminate those long lists of trusted third-party scripts

• Consider using script-src 'report-sample' as it significantly helps debugging CSP reports. See specification