Security

· 12 checks — HTTP headers, CSP, TLS handshake, and cookie hygiene rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Checks

5 PASS 2 REVIEW 5 FIX

Security Headers

Action

3 of 10 headers properly configured

FIX

3 of 10 headers properly configured

Strict-Transport-Security is properly configured

Got: max-age=31536000; includeSubDomains; preload

X-Content-Type-Options header is missing

This header prevents MIME-type sniffing, which can lead to XSS attacks. Set it to 'nosniff'.

Expected: nosniff

X-Frame-Options header is missing

This header prevents clickjacking by controlling who can embed your page in a frame. Set it to DENY or SAMEORIGIN.

Expected: DENY

Referrer-Policy header is missing

Controls how much referrer information is sent with requests. Set to 'strict-origin-when-cross-origin' or stricter.

Expected: strict-origin-when-cross-origin

Permissions-Policy header is missing

Controls which browser features (camera, microphone, geolocation) are allowed. Set it to restrict unused features.

Expected: geolocation=(), camera=(), microphone=()

Content-Security-Policy is present

Got: frame-ancestors 'self' https://*.substack.com https://substack.com

Cross-Origin-Opener-Policy header is missing

COOP isolates your browsing context, preventing cross-origin side-channel attacks. Set to 'same-origin'.

Expected: same-origin

Cross-Origin-Embedder-Policy header is missing

COEP prevents loading cross-origin resources without explicit permission. Required for SharedArrayBuffer and high-resolution timers.

Expected: require-corp

X-Powered-By header reveals technology stack

This header discloses server technology (e.g. Express, PHP), helping attackers target known vulnerabilities. Remove it.

Got: Express

Server header is present without version info

Got: cloudflare

This header prevents MIME-type sniffing, which can lead to XSS attacks. Set it to 'nosniff'.

Expected: nosniff

Why this matters

MIME sniffing lets browsers run uploaded files as JavaScript, turning a file upload into an XSS.

Learn more ▾

Setting X-Content-Type-Options: nosniff tells browsers to trust your declared Content-Type instead of guessing. Without it, an attacker who uploads a polyglot file can sometimes get it executed as a script. One header, no downside.

Source: OWASP / MDN

This header prevents clickjacking by controlling who can embed your page in a frame. Set it to DENY or SAMEORIGIN.

Expected: DENY

Why this matters

Without frame protection, your site can be embedded in a hostile page and used for clickjacking.

Learn more ▾

Clickjacking overlays your site under a transparent malicious page so users click invisible buttons. Setting X-Frame-Options: DENY (or a modern frame-ancestors CSP directive) blocks the embedding entirely. There's almost never a legitimate reason to allow it.

Source: OWASP / MDN

Controls how much referrer information is sent with requests. Set to 'strict-origin-when-cross-origin' or stricter.

Expected: strict-origin-when-cross-origin

Why this matters

Default browser behavior leaks full URLs (including query params and tokens) to every third-party resource — set a strict policy.

Learn more ▾

Without a Referrer-Policy header, browsers send the full referring URL with images, scripts, and fonts loaded from third-party origins. URLs containing tokens, user IDs, or session params end up in third-party logs. Set `Referrer-Policy: strict-origin-when-cross-origin` (or stricter) to limit leakage.

Source: MDN / W3C

Controls which browser features (camera, microphone, geolocation) are allowed. Set it to restrict unused features.

Expected: geolocation=(), camera=(), microphone=()

Why this matters

Permissions-Policy locks down browser APIs you don't use — without it, every page can request camera/mic/geolocation if XSS lands.

Learn more ▾

By default every page can request the camera, microphone, geolocation, payment APIs, and dozens more. Permissions-Policy turns off the ones you don't need so a future bug can't quietly start using them. It's a defense-in-depth header — one line, big surface reduction.

Source: MDN / W3C

COOP isolates your browsing context, preventing cross-origin side-channel attacks. Set to 'same-origin'.

Expected: same-origin

Why this matters

COOP isolates your top-level browsing context from cross-origin windows — without it, popup-based side-channel attacks remain possible.

Learn more ▾

Cross-Origin-Opener-Policy: same-origin prevents cross-origin pages from sharing a browsing-context group with yours. This blocks cross-window references that enable Spectre-style timing attacks and tab-nabbing. Required if you want to enable SharedArrayBuffer.

Source: MDN / web.dev

COEP prevents loading cross-origin resources without explicit permission. Required for SharedArrayBuffer and high-resolution timers.

Expected: require-corp

Why this matters

COEP enforces that all embedded resources opt-in to cross-origin embedding — required for cross-origin isolation features.

Learn more ▾

Cross-Origin-Embedder-Policy: require-corp ensures every embedded resource (script, iframe, image) explicitly allows being loaded cross-origin. Combined with COOP, this enables the cross-origin-isolated context that unlocks SharedArrayBuffer, high-resolution timers, and other powerful APIs.

Source: MDN / web.dev

This header discloses server technology (e.g. Express, PHP), helping attackers target known vulnerabilities. Remove it.

Why this matters

X-Powered-By: PHP/7.4.3 advertises your stack to attackers — disable it.

Learn more ▾

X-Powered-By and similar headers (X-AspNet-Version, X-Runtime) tell attackers which versions to target. Disable in your server/framework config: PHP `expose_php=Off`, ASP.NET `<httpRuntime enableVersionHeader="false">`, Express `app.disable('x-powered-by')`.

Source: OWASP

Cookie Security

Action

8 cookies analyzed, 13 checks passed

FIX

8 cookies analyzed, 13 checks passed

Cookie 'ab_experiment_sampled' has the Secure flag

Cookie 'ab_experiment_sampled' has the HttpOnly flag

Cookie 'ab_experiment_sampled' has SameSite=Lax

Cookie 'ab_testing_id' has the Secure flag

Cookie 'ab_testing_id' has the HttpOnly flag

Cookie 'ab_testing_id' has SameSite=Lax

Cookie 'AWSALBTG' is missing the Secure flag

Without the Secure flag, this cookie can be sent over unencrypted HTTP, exposing it to interception.

Cookie 'AWSALBTG' is missing the HttpOnly flag

Without HttpOnly, this cookie can be accessed by JavaScript, making it vulnerable to XSS-based theft.

Cookie 'AWSALBTG' has no SameSite attribute

Without an explicit SameSite attribute, browser default behavior varies. Set SameSite=Lax or Strict.

Cookie 'AWSALBTGCORS' has the Secure flag

Cookie 'AWSALBTGCORS' is missing the HttpOnly flag

Without HttpOnly, this cookie can be accessed by JavaScript, making it vulnerable to XSS-based theft.

Cookie 'AWSALBTGCORS' has SameSite=None

Cookie 'cookie_storage_key' has the Secure flag

Cookie 'cookie_storage_key' is missing the HttpOnly flag

Without HttpOnly, this cookie can be accessed by JavaScript, making it vulnerable to XSS-based theft.

Cookie 'cookie_storage_key' has SameSite=None

Cookie 'disable_html_pixels' is missing the Secure flag

Without the Secure flag, this cookie can be sent over unencrypted HTTP, exposing it to interception.

Cookie 'disable_html_pixels' is missing the HttpOnly flag

Without HttpOnly, this cookie can be accessed by JavaScript, making it vulnerable to XSS-based theft.

Cookie 'disable_html_pixels' has no SameSite attribute

Without an explicit SameSite attribute, browser default behavior varies. Set SameSite=Lax or Strict.

Cookie 'disable_experiments' is missing the Secure flag

Without the Secure flag, this cookie can be sent over unencrypted HTTP, exposing it to interception.

Cookie 'disable_experiments' is missing the HttpOnly flag

Without HttpOnly, this cookie can be accessed by JavaScript, making it vulnerable to XSS-based theft.

Cookie 'disable_experiments' has no SameSite attribute

Without an explicit SameSite attribute, browser default behavior varies. Set SameSite=Lax or Strict.

Cookie '__cf_bm' has the Secure flag

Cookie '__cf_bm' has the HttpOnly flag

Cookie '__cf_bm' has SameSite=None

8 cookies analyzed 3 critical 8 warnings

Name	Secure	HttpOnly	SameSite	Size	Issues
ab_experiment_sampled	✓	✓	Lax	32 B	—
ab_testing_id	✓	✓	Lax	55 B	—
AWSALBTG	✗	✗	—	180 B	3
AWSALBTGCORS	✓	✗	None	184 B	1
cookie_storage_key	✓	✗	None	54 B	1
disable_html_pixels	✗	✗	—	20 B	3
disable_experiments	✗	✗	—	20 B	3
__cf_bm	✓	✓	None	177 B	—

Subresource Integrity

Action

0 of 151 external resources have SRI

FIX

0 of 151 external resources have SRI

External link from substackcdn.com lacks integrity attribute