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Application & OT Security · Intermediate

X-Content-Type-Options

An HTTP response header whose nosniff value stops browsers from MIME-sniffing a response away from its declared Content-Type.

Definition

Without nosniff, a browser might interpret an uploaded text file as script or HTML, enabling XSS. Setting X-Content-Type-Options: nosniff together with correct Content-Type headers prevents this.

Example

X-Content-Type-Options: nosniff

Exam tip

Only valid value is nosniff; it defends against MIME confusion attacks.

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