Mozilla Foundation Security Advisory 2015-24

Reading of local files through manipulation of form autocomplete

February 24, 2015
Armin Ebert
Firefox, Firefox ESR, Firefox OS, SeaMonkey, Thunderbird
Fixed in
  • Firefox 36
  • Firefox ESR 31.5
  • Firefox OS 2.2
  • SeaMonkey 2.33
  • Thunderbird 31.5


Security researcher Armin Ebert reported that a user readable file in a known local path could be uploaded to a malicious site. This was done by manipulating the autocomplete feature in a form and user interaction with it. While the local file is not visibly uploaded through the form, its contents are made available through the Document Object Model (DOM) to script content on the attacking page, leading to information disclosure.

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.