module: std
package: net/http/fcgi
versions:
  - fixed: go1.14.8
  - fixed: go1.15.1
description: |
    When a Handler does not explicitly set the Content-Type header, the the
    package would default to “text/html”, which could cause a Cross-Site Scripting
    vulnerability if an attacker can control any part of the contents of a
    response.

    The Content-Type header is now set based on the contents of the first Write
    using http.DetectContentType, which is consistent with the behavior of the
    net/http package.

    Although this protects some applications that validate the contents of
    uploaded files, not setting the Content-Type header explicitly on any
    attacker-controlled file is unsafe and should be avoided.
cves:
  - CVE-2020-24553
credit: RedTeam Pentesting GmbH
symbols:
  - response.Write
  - response.WriteHeader
  - response.writeCGIHeader
links:
    pr: https://go.dev/cl/252179
    commit: https://go.googlesource.com/go/+/4f5cd0c0331943c7ec72df3b827d972584f77833
    context:
      - https://groups.google.com/g/golang-announce/c/8wqlSbkLdPs
      - https://go.dev/issue/40928