Mozilla Foundation Security Advisory 2006-56

chrome: scheme loading remote content

July 25, 2006
Benjamin Smedberg (Mozilla)
Firefox, SeaMonkey, Thunderbird
Fixed in
  • Firefox
  • SeaMonkey 1.0.3
  • Thunderbird


Benjamin Smedberg discovered that chrome URL's could be made to reference remote files, which would run scripts with full privilege. There is no known way for web content to successfully load a chrome: url, but if a user could be convinced to do so manually (perhaps by copying a link and pasting it into the location bar) this could be exploited.

Although Thunderbird shares the browser engine with Firefox it supports no way for a mail message to load a chrome: url or to cause one to be loaded in the browser. It is thus not vulnerable to this flaw. The underlying Thunderbird code has been fixed in


Do not copy or drag links from untrusted web content or emails. If you must, make sure it is a normal http:, https:, or ftp: link rather than chrome: or another uncommon type.

Disabling JavaScript would prevent remote chrome pages from running any exploit code, but that should not be necessary since there is no known way to load a chrome: url in a browser window without the user doing so manually by entering it in the location bar.


Exploit details withheld during the active upgrade period