Matan · Security · Headers

X-Content-Type-Options

nosniff stops the browser from guessing MIME types.

Pass condition in our engine: X-Content-Type-Options includes nosniff.

1. Problem description

MIME sniffing historically turned a user-uploaded text file into executable HTML. nosniff is a one-line header with almost no compatibility cost.

2. Most common causes

  • The app platform does not send it by default.

3. How to fix it

  1. Add X-Content-Type-Options: nosniff on all responses.
  2. Serve correct Content-Type as well.

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