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The Anti-MIME-Sniffing header X-Content-Type-Options is missing or not set to nosniff. This allows older versions of Internet Explorer and Chrome to perform MIME-sniffing on the response body, potentially causing the response body to be interpreted and displayed as a content type other than the declared content type. Current and legacy versions of Firefox will use the declared content type (if one is set), rather than performing MIME-sniffing.


Ensure that the application/web server sets the Content-Type header appropriately and that it sets the X-Content-Type-Options header to nosniff for all web pages. If possible, ensure that the end user uses a standards-compliant and modern web browser that does not perform MIME-sniffing at all or that can be directed by the web application/web server to not perform MIME-sniffing.

GraphQL Specific


When using Apollo with Express.js, helmet can take care of the security headers.

const helmet = require("helmet");
  • Add security headers with the API Gateway

Put your AppSync API behind an API Gateway and configure it to act as a proxy to your AppSync endpoint (e.g., using the HTTP Proxy feature).

API Gateway Documentation

Then you can manually add headers to each resource. (There is only one resource if your API Gateway is only used to proxy a single AppSync endpoint)

Here is an example of security headers you can add :

Cache-Control: no-store
Content-Security-Policy: default-src 'self'
Strict-Transport-Security: max-age=63072000
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
  • Add security headers using only AWS AppSync

AWS AppSync currently does not allow to append custom headers to every response.

However, custom response headers can be configured individually for every resolver by using response mapping templates.

To do this, go to:

  • AppSync > {Your App} > Schema

For every attached resolver :

  • Go to the resolver configuration
  • In the "Configure the response mapping template" section, add this :
$util.http.addResponseHeader("Cache-Control", "no-store")
$util.http.addResponseHeader("Content-Security-Policy", "default-src 'self'")
$util.http.addResponseHeader("Strict-Transport-Security", "max-age=63072000")
$util.http.addResponseHeader("X-Content-Type-Options", "nosniff")
$util.http.addResponseHeader("X-Frame-Options", "SAMEORIGIN")
$util.http.addResponseHeader("X-XSS-Protection", "1; mode=block")

You can safely ignore this warning if you did this for every single resolver.

However, it may still appear here as GraphQL requests like query { __typename } are not associated with a resolver; therefore, you cannot add custom response headers. (Which doesn't matter as such requests cannot leak data as no actual field is queried)

AWS AppSync adds support for custom response headers

HTTP helpers in $util.http

Resolver Mapping Template Programming Guide


You can use a HTTP middleware to add security headers.

For instance, with srikrsna/security-headers:

import (
secure ""

h := handler.New(&handler.Config{
Schema: &schema,

s := &secure.Secure{
STSIncludeSubdomains: true,
STSPreload: true,
STSMaxAgeSeconds: 90,

FrameOption: secure.FrameAllowFrom,
FrameOrigin: "",

ContentTypeNoSniff: true,

XSSFilterBlock: true,

HPKPPins: []string{
HPKPMaxAge: 5184000,
HPKPReportURI: "",
HPKPIncludeSubdomains: true,

ExpectCTMaxAge: 5184000,
ExpectCTEnforce: true,
ExpectCTReportUri: "",

ReferrerPolicy: secure.ReferrerStrictOriginWhenCrossOrigin,
http.Handle("/graphql", s.Middleware()(h))

http.ListenAndServe(":8082", nil)

To add Security Headers to Django, follow this guide :

How to Score A+ for Security Headers on Your Django Website

For Flask, use Google's flask-talisman


Identifier: protocol/header_x_content_type_options


Ignore this check

"checks": {
"protocol/header_x_content_type_options": {
"skip": true


  • Escape Severity: LOW
    • OWASP: API7:2023
    • PCI DSS: 6.5.10
    • CWE
      • 693
      • 732
      • 1004
      • 1275
    • WASC: WASC-15


  • CVSS_SCORE: 5.1