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Mozilla Foundation Security Advisory 2013-54

Title: Data in the body of XHR HEAD requests leads to CSRF attacks
Impact: High
Announced: June 25, 2013
Reporter: Johnathan Kuskos
Products: Firefox, Thunderbird, Seamonkey

Fixed in: Firefox 22.0
  Firefox ESR 17.0.7
  Thunderbird 17.0.7
  Thunderbird ESR 17.0.7
  SeaMonkey 2.19


Security researcher Johnathan Kuskos reported that Firefox is sending data in the body of XMLHttpRequest (XHR) HEAD requests, which goes agains the XHR specification. This can potentially be used for Cross-Site Request Forgery (CSRF) attacks against sites which do not distinguish between HEAD and POST requests.

In general these flaws cannot be exploited through email in the Thunderbird and SeaMonkey products because scripting is disabled, but are potentially a risk in browser or browser-like contexts in those products.