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Mozilla Foundation Security Advisory 2015-37

CORS requests should not follow 30x redirections after preflight

Announced
March 31, 2015
Reporter
Christoph Kerschbaumer, Muneaki Nishimura
Impact
High
Products
Firefox, Firefox ESR, Firefox OS, SeaMonkey, Thunderbird
Fixed in
  • Firefox 37
  • Firefox ESR 31.6
  • Firefox OS 2.2
  • SeaMonkey 2.35
  • Thunderbird 31.6

Description

Mozilla developer Christoph Kerschbaumer discovered an issue while investigating Mozilla Foundation Security Advisory 2015-03, previously reported by security researcher Muneaki Nishimura. This flaw was that a cross-origin resource sharing (CORS) request should not follow 30x redirections after preflight according to the specification. This only affects sendBeacon() requests but could allow for a potential Cross-site request forgery (XSRF) attack from malicious websites.

In general this flaw cannot be exploited through email in the Thunderbird product because scripting is disabled, but is potentially a risk in browser or browser-like contexts.

References