Firefox 0.9.2, Thunderbird 0.7.2, Mozilla 1.7.1 Coming Soon

Thursday July 8th, 2004

Branches have been created for three of's latest releases, in order to fix an external Windows protocol handler bug. The fix involves disabling the shell: protocol handler, which was found to enable pages to run executables on Windows via a link. Builds should officially be available shortly, and there will also be an XPI offered to disable the pref. Alternatively, you can set the pref in about:config to false to remove the exploit. (This will only set it on your current profile, if you have more than one profile, or could be creating more, you should use the XPI or the updated build.)

More information about the exploit can be found in this post on the FullDisclosure mailing list.

Update: The XPI to disable the pref is now available.

Another Update: has published a document on the issue.

Yet Another Update: There is an eWeek article about the exploit as well as a discussion at Slashdot. The now public bug report that covers the shell: vulnerability is bug 250180 (no unnecessary comments please). Some may find it notable that a patch was issued less than forty-eight hours after this bug was filed.

Yet Another Update: If you are not using Windows, you are not at risk from this bug. If you are using Windows, go to to see if you are vulnerable.

#50 Found Easy Workaround at

by ivyvine

Saturday July 31st, 2004 8:25 PM

You are replying to this message

Hi again--

Apparently the following will work just as easily as downloading the .xpi file (found this info at

Workarounds Disable the shell: protocol handler Mozilla and Firefox users, particularly those who are unable to apply the patches supplied by the Mozilla Project, are encouraged to consider disabling the shell: protocol handler. This can be accomplished by adding the following line to the prefs.js file: user_pref("", false);

Will edit the prefs.js file as described.

BUT: Again, I ask:

Isn't there somewhere in WINDOWS itself where we can disable this shell: protocol handler? What does the average person use Shell: protocol for? If we do not use TelNet and similar programs, do we need shell?

Thanks in advance for any clarification anyone can provide.