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Mozilla Foundation Security Advisory 2011-40

Title: Code installation through holding down Enter
Impact: Critical
Announced: September 27, 2011
Reporter: Mariusz Mlynski
Products: Firefox, Thunderbird, SeaMonkey

Fixed in: Firefox 7.0
  Firefox 3.6.23
  Thunderbird 7.0
  Thunderbird 3.1.15
  SeaMonkey 2.4


Mariusz Mlynski reported that if you could convince a user to hold down the Enter key--as part of a game or test, perhaps--a malicious page could pop up a download dialog where the held key would then activate the default Open action. For some file types this would be merely annoying (the equivalent of a pop-up) but other file types have powerful scripting capabilities. And this would provide an avenue for an attacker to exploit a vulnerability in applications not normally exposed to potentially hostile internet content.

Mariusz also reported a similar flaw with manual plugin installation using the PLUGINSPAGE attribute. It was possible to create an internal error that suppressed a confirmation dialog, such that holding enter would lead to the installation of an arbitrary add-on. (This variant did not affect Firefox 3.6)