Mastodon

Meets the B minimum (70/100) in our RFP clause.

With these headers missing, joinmastodon.org is more exposed to hijacked payments and clickjacking.

Missing 3

• Frame protection 0 of 10

  X-Frame-Options or the CSP frame-ancestors directive: decides which sites may show this one inside a frame.

  Without it: Clickjacking. Another site loads the product invisibly in a frame and lines its real buttons up under something the user wants to click, so a signed-in user approves a payment, changes their account email or grants access without seeing it.

• Cross-Origin-Opener-Policy 0 of 5

  Cuts the link between the product's window and windows opened by, or opening, other sites.

  Without it: A page that opens the product keeps a handle on its window and can later redirect it to a look-alike sign-in or payment page (tab-nabbing) while the user thinks they are still on the real site. It is also part of the isolation browsers need to defend against Spectre-style attacks.

• Cross-Origin-Resource-Policy 0 of 5

  Tells browsers which sites may load this site's resources.

  Without it: Other sites can pull the product's responses into their own pages, which makes side-channel leaks of what a signed-in user can see easier.

Sent 6

• Content-Security-Policy 25 of 25

  default-src 'self'; child-src 'self'; object-src 'none'; img-src 'self' proxy.joinmastodon.org blob: data:; style-src 'self' 'unsafe-inline'; script-src 'self'; connect-src 'self' api.joinmastodon.org; block-all-mixed-content

• Strict-Transport-Security 20 of 20

  max-age=31536000; includeSubDomains; preload

• X-Content-Type-Options 10 of 10

  nosniff

• Referrer-Policy 10 of 10

  origin-when-cross-origin

• Permissions-Policy 10 of 10

  camera=(), microphone=(), geolocation=(), browsing-topics=()

• No version disclosure 5 of 5

Checked 2026-10-21 at https://joinmastodon.org/. Re-checked every 7 days. The grade covers the headers this website sends, not the product’s overall security. How the grade works.