Mozilla Foundation Security Advisory 2015-100

Arbitrary file manipulation by local user through Mozilla updater

September 22, 2015
Holger Fuhrmannek
Firefox, Firefox ESR, Thunderbird
Fixed in
  • Firefox 41
  • Firefox ESR 38.3
  • Thunderbird 38.3


Security researcher Holger Fuhrmannek reported that when the Mozilla updater is run, the updater can be manipulated to load the updated files from a working directory under user control in concert with junctions. When the updates are run by the Mozilla Maintenance Service on Windows, these malicious files can be run with elevated privileges and be used to replace arbitrary files on the system. This could allow for arbitrary code execution by a malicious user with local system access but does not allow for exploitation by web content.

This issue is specific to Windows and does not affect Linux or OS X systems.