TUCoPS :: Browsers :: hack8010.htm

Firesearching 1 + 2 [mikx]
Firesearching 1 + 2 [Firefox 1.0.2]


I really wonder why the Mozilla Foundation decided to release a serious 
security update on a friday night and to disclose the link to my 
proof-of-concept code so quickly. It wasn't intendet from my side to release 
this as a 0day exploit. Please complain to security@mozilla.org if you 
disagree with their release policy.


The search plugin technology in Firefox is based on Apple's sherlock files, 
a simple text format to syndicate a search engine interface. The installer 
and parser of those files contain design bugs that allow to create a search 
eninge that works as a spyware tool and/or execution vehicle for arbitrary 

Firesearching 1

By creating a special sherlock file it is possible to run javascript code in 
the security context of the currently active tab. This allows to create 
search engines that silently monitor all website displayed while searching 
(e.g. to steal sessions cookies) and/or that wait for a privileged page 
(e.g. chrome or about:config) to run arbitrary code.

The demo adds a new search engine (called Firesearching) by calling 
sidebar.addSearchEngine() that behaves like a normal Google search. When 
searching with that engine an alert shows that the engine has javascript 
access to the currently active tab. An attacker could silently send the 
information to another host instead.

Firesearching 2

By creating a special sherlock file it is possible to overwrite an existing 
search engine without a chance for the user to see what is going on. The 
displayed name in the confirmation dialog is given as the third parameter of 
sidebar.addSearchEngine(), but the displayed name in the search dropdown is 
taken from the sherlock file. This way it is possible to overwrite the 
default Google search with a modified version that monitors the data and/or 
waits for a chance to run code. The string "google.src" in the source URL 
got also be moved out of the dialog by supplying a really long URL to the 
sherlock file (the dialog just cuts the source URL when it's getting too 

The user will probably think the search engine installation just failed, 
because after confirming the installation dialog Firefox never displays an 
error messages if the installation failed because e.g. the sherlock file is 
broken or not found. Since there is no UI to see details about the installed 
searches a common user will probably never find out that the default Google 
search got modified. Using the built in sherlock update feature an attacker 
also gets a decent update mechanism to modifiy the scripts beyond the 
initial infection.




The bugs are fixed in Firefox 1.0.3. Don't install search plugins as a 

2005-04-12 Vendor informed (bugzilla.mozilla.org #290037 and #290038)
2005-04-12 Vendor confirmed bug
2005-04-15 Vendor published fix, advisory and link to PoC (mfsa2005-38)
2005-04-18 This advisory

__Affected Software

Tested with Firefox 1.0.2

__Contact Informations

Michael Krax  


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