bungee.host

What is this?

CAA (Certification Authority Authorization) is a DNS record that specifies which Certificate Authorities (CAs) are allowed to issue SSL/TLS certificates for your domain.

Why does it matter?

Without CAA records, any of the hundreds of trusted CAs worldwide can issue a certificate for your domain. A compromised or rogue CA could issue a fraudulent certificate for your domain, enabling MITM attacks. CAA limits this risk to your chosen CA(s).

How to fix it

Add CAA records to your DNS. Example for Let\'s Encrypt only: 0 issue "letsencrypt.org" For multiple CAs (e.g. Let\'s Encrypt + DigiCert): 0 issue "letsencrypt.org" 0 issue "digicert.com" To also allow wildcard certificates: 0 issuewild "letsencrypt.org" For email notifications on unauthorized issuance attempts: 0 iodef "mailto:security@yourdomain.com" Check current CAA records at: sslmate.com/caa

What is this?

MTA-STS (Mail Transfer Agent Strict Transport Security) is a standard that forces other mail servers to use encrypted TLS connections when delivering email to your domain. Without it, a network attacker could silently strip TLS from email in transit.

Why does it matter?

Email is delivered between servers using SMTP. By default, SMTP tries TLS but falls back to plaintext if TLS is not available — a downgrade attack. MTA-STS prevents this fallback, ensuring all email delivered to your domain is encrypted in transit.

How to fix it

Implementing MTA-STS requires two things: 1. A DNS TXT record at _mta-sts.yourdomain.com: v=STSv1; id=20240101001 2. A policy file hosted at: https://mta-sts.yourdomain.com/.well-known/mta-sts.txt Policy file content: version: STSv1 mode: enforce mx: mail.yourdomain.com max_age: 86400 Start with mode: testing to see reports before enforcing. Use mta-sts.io for a guided setup.

What is this?

Subresource Integrity (SRI) is a browser security feature that lets you specify a cryptographic hash for external scripts and stylesheets. The browser refuses to execute the resource if its content does not match the hash.

Why does it matter?

If a CDN you rely on is compromised (a real and recurring attack vector), an attacker can replace your JavaScript library with malicious code that steals user data, injects cryptomining scripts, or performs other attacks. SRI prevents this by making the browser verify the file has not been altered.

How to fix it

Add integrity= and crossorigin= attributes to your external resources: <script src="https://cdn.jsdelivr.net/npm/jquery@3.7.1/dist/jquery.min.js" integrity="sha256-/JqT3SQfawRcv/BIHPThkBvs0OEvtFFmqPF/lYI/Cxo=" crossorigin="anonymous" ></script> Generate hashes for any URL at: https://www.srihash.org/ For build tools, use webpack-subresource-integrity or vite-plugin-sri to add hashes automatically during builds.

What is this?

Content Security Policy (CSP) is a browser security feature that lets you control which resources (scripts, styles, images, fonts) a page is allowed to load, and from which origins.

Why does it matter?

CSP is one of the most effective defences against Cross-Site Scripting (XSS) attacks. Without CSP, an attacker who injects malicious JavaScript into your page can load resources from anywhere, steal session cookies, or redirect users.

How to fix it

Add a Content-Security-Policy header. Start with a report-only policy to detect issues without breaking anything: Content-Security-Policy-Report-Only: default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; Once tested, switch to enforcing: Content-Security-Policy: default-src 'self'; ... CSP policies can be complex for sites with third-party scripts. Use https://csp-evaluator.withgoogle.com/ to evaluate your policy.

What is this?

The Referrer-Policy header controls how much information about the originating page is included in the Referer header when a user navigates away from your site or when resources are loaded.

Why does it matter?

Without a Referrer-Policy, the full URL of the current page (which may include session tokens, user IDs, or sensitive paths) is sent to external sites in the Referer header. This can leak private information to third-party analytics, CDN providers, or ad networks.

How to fix it

Recommended value: Referrer-Policy: strict-origin-when-cross-origin (sends origin only for cross-origin requests, full URL for same-origin) Nginx: add_header Referrer-Policy "strict-origin-when-cross-origin" always; Apache: Header always set Referrer-Policy "strict-origin-when-cross-origin" Alternatives: no-referrer (most private), same-origin (no cross-origin referrer).

What is this?

Permissions-Policy (formerly Feature-Policy) lets you control which browser features and APIs your site is allowed to use, and whether third-party content embedded in iframes can access them.

Why does it matter?

Without this header, embedded third-party scripts or iframes could theoretically request access to the camera, microphone, geolocation, payment APIs, and more. Restricting these features reduces your attack surface.

How to fix it

Example header that disables features not needed for most sites: Permissions-Policy: camera=(), microphone=(), geolocation=(), payment=() Nginx: add_header Permissions-Policy "camera=(), microphone=(), geolocation=()" always; Apache: Header always set Permissions-Policy "camera=(), microphone=(), geolocation=()" Only disable features you genuinely don't use. Adding this header is a low-effort, high-value improvement.