Public Vulnerability Reports

Predictable Directory Structure Allows Theft of Netscape Preferences File



Netscape Communications Corp.'s Communicator is a popular web-browsing package that includes a web browser (Navigator), e-mail client, news client, and address book.


Socially engineering users of Netscape Communicator 4.x's web browser and e-mail client into clicking on a malicious link could return the contents of the targeted user's preferences file back to a remote attacker.

The attack involves the redefinition of user_pref(), which is an internal JavaScript function. The redefined function constructs a string of all user preferences stored in the hidden field of a form and later submitted by another JavaScript routine. In order for the redefinition to occur, an attacker must store the exploit script in a Windows (or Samba) share and coerce a victim into following a link to it. A sample link to an attack script would look like file:///  Communicator only allows local
files to redefine internal functions.


Remote exploitation allows an attacker to steal user preferences, including the victim's real name, e-mail address, e-mail server, URL history and, in some cases, e-mail password.


Netscape Communicator 4.x is vulnerable. Communicator 6 and later is not vulnerable, being it stores the prefs.js file in a randomized location.


The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project assigned the identification number CAN-2002-1204 to this issue.


08/29/2002 Issue disclosed to iDEFENSE
10/14/2002 Netscape notified (,
10/14/2002 iDEFENSE clients notified
10/31/2002 Second attempt at vendor contact
11/07/2002 Third attempt at vendor contact
11/19/2002 Public disclosure


Bennett Haselton ( discovered this vulnerability.