Mozilla Privacy Bug

Saturday September 14th, 2002

Yesterday, ZDNet UK News reported that Mozilla has a privacy flaw involving HTTP referers. The flaw can be exploited using the onUnload JavaScript handler, which is triggered when a visitor leaves a page (for example, by clicking a link or using a bookmark). The problem is that the referer Mozilla sends is the URL of the page that the visitor is going to, not the page that he or she is exiting. This means that a site can discover where you are heading when you leave.

The security bug is present in the latest versions of Mozilla (including 1.0.1, 1.1 and 1.2 Alpha) as well as some Mozilla-based browsers, such as Netscape 6.x, Netscape 7.0, Galeon 1.2.x and Chimera 0.5. At the time of writing, no fix is available. A workaround is to disable JavaScript (Edit > Preferences > Advanced > Scripts & Plugins).

A demonstration of the exploit has been created by security researcher Sven Neuhaus, who posted details of the vulnerability to Bugtraq on Wednesday.

The bug was filed in Bugzilla as bug 145579 on Sunday 19th May, with the more serious onUnload behaviour found on Friday 7th June. The report is currently marked as "Security-Sensitive" and access to it is restricted in line with the Mozilla Security Bugs Policy.

UPDATE! Bug 145579 has now been made public.

ANOTHER UPDATE! A fix has been checked in to the trunk. A patch for the 1.0 branch will follow shortly.

YET ANOTHER UPDATE! A patch has now been checked in to the 1.0 branch.

#20 Security flaws

by amutch

Monday September 16th, 2002 1:29 AM

You are replying to this message


I use Mozilla and Mozilla-based browsers almost exclusively and have never been struck by security flaws in any of them. I also support a Mozilla-based browser at work for public access computers and I have NEVER had a security problem with it in 1.5 years of use. On the other hand, I also have to support Internet Explorer at work and I am constantly having to fend off the security holes in IE. Things have settled down a bit with Windows 2000 versus Windows 98, which was a security nightmare, but I still have to download and install "critical" patches on a weekly basis with IE. That's real-world experience. Maybe you can share your experiences that would convince me to abandon Mozilla for IE's bugginess.