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Firefox Privacy Notice

Mozilla Foundation Security Advisory 2014-09

Cross-origin information leak through web workers

February 4, 2014
Masato Kinugawa
Firefox, Firefox ESR, SeaMonkey, Thunderbird
Fixed in
  • Firefox 27
  • Firefox ESR 24.3
  • SeaMonkey 2.24
  • Thunderbird 24.3


Security researcher Masato Kinugawa reported a cross-origin information leak through web workers' error messages. This violates same-origin policy and the leaked information could potentially be used to gather authentication tokens and other data from third-party websites.

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