Headers Security
medium Severity
Free Check

X-Content-Type-Options Header

Prevents browsers from MIME-sniffing a response away from the declared content-type, stopping script execution from uploads.

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Why It Matters

If an attacker uploads an image file containing JavaScript, MIME-sniffing could execute it as executable code in the victim’s browser.

How We Check This

We check if X-Content-Type-Options is sent with the exact value nosniff.

How to Fix & Implement

Copy-paste configuration blocks tailored for your web server or edge proxy.

nginx snippet
add_header X-Content-Type-Options "nosniff" always;

Frequently Asked Questions

What is MIME-sniffing?

MIME-sniffing is when a browser inspects file bytes instead of relying on the Content-Type header to guess its type.